[lower bounds] embedded_ocaml_templates need upper bound on ppxlib

[mseri]

#=== ERROR while compiling embedded_ocaml_templates.0.3.1 =====================#
# context              2.0.9 | linux/x86_64 | ocaml-base-compiler.4.12.1 | file:///home/opam/opam-repository
# path                 ~/.opam/4.12/.opam-switch/build/embedded_ocaml_templates.0.3.1
# command              ~/.opam/opam-init/hooks/sandbox.sh build dune build -p embedded_ocaml_templates -j 31
# exit-code            1
# env-file             ~/.opam/log/embedded_ocaml_templates-19827-e7966f.env
# output-file          ~/.opam/log/embedded_ocaml_templates-19827-e7966f.out
### output ###
#       ocamlc src/.ppx_eml.objs/byte/ppx_eml.{cmo,cmt} (exit 2)
# (cd _build/default && /home/opam/.opam/4.12/bin/ocamlc.opt -w -40 -g -bin-annot -I src/.ppx_eml.objs/byte -I /home/opam/.opam/4.12/lib/base -I /home/opam/.opam/4.12/lib/base/base_internalhash_types -I /home/opam/.opam/4.12/lib/base/caml -I /home/opam/.opam/4.12/lib/base/md5 -I /home/opam/.opam/4.12/lib/base/shadow_stdlib -I /home/opam/.opam/4.12/lib/base_bigstring -I /home/opam/.opam/4.12/lib/base_quickcheck -I /home/opam/.opam/4.12/lib/bin_prot -I /home/opam/.opam/4.12/lib/bin_prot/shape -I /home/opam/.opam/4.12/lib/bytes -I /home/opam/.opam/4.12/lib/containers -I /home/opam/.opam/4.12/lib/containers/monomorphic -I /home/opam/.opam/4.12/lib/core -I /home/opam/.opam/4.12/lib/core/error_checking_mutex -I /home/opam/.opam/4.12/lib/core_kernel -I /home/opam/.opam/4.12/lib/core_kernel/base_for_tests -I /home/opam/.opam/4.12/lib/core_kernel/caml_unix -I /home/opam/.opam/4.12/lib/core_kernel/flags -I /home/opam/.opam/4.12/lib/core_kernel/version_util -I /home/opam/.opam/4.12/lib/fieldslib -I /home/opam/.opam/4.12/lib/gen -I /home/opam/.opam/4.12/lib/jane-street-headers -I /home/opam/.opam/4.12/lib/menhirLib -I /home/opam/.opam/4.12/lib/ocaml-compiler-libs/common -I /home/opam/.opam/4.12/lib/ocaml-compiler-libs/shadow -I /home/opam/.opam/4.12/lib/ocaml/compiler-libs -I /home/opam/.opam/4.12/lib/ocaml/threads -I /home/opam/.opam/4.12/lib/parsexp -I /home/opam/.opam/4.12/lib/ppx_assert/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_bench/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_compare/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_derivers -I /home/opam/.opam/4.12/lib/ppx_enumerate/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_expect/collector -I /home/opam/.opam/4.12/lib/ppx_expect/common -I /home/opam/.opam/4.12/lib/ppx_expect/config -I /home/opam/.opam/4.12/lib/ppx_expect/config_types -I /home/opam/.opam/4.12/lib/ppx_hash/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_here/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_inline_test/config -I /home/opam/.opam/4.12/lib/ppx_inline_test/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_module_timer/runtime -I /home/opam/.opam/4.12/lib/ppx_sexp_conv/runtime-lib -I /home/opam/.opam/4.12/lib/ppxlib -I /home/opam/.opam/4.12/lib/ppxlib/ast -I /home/opam/.opam/4.12/lib/ppxlib/astlib -I /home/opam/.opam/4.12/lib/ppxlib/print_diff -I /home/opam/.opam/4.12/lib/ppxlib/stdppx -I /home/opam/.opam/4.12/lib/ppxlib/traverse_builtins -I /home/opam/.opam/4.12/lib/sedlex -I /home/opam/.opam/4.12/lib/seq -I /home/opam/.opam/4.12/lib/sexplib -I /home/opam/.opam/4.12/lib/sexplib/unix -I /home/opam/.opam/4.12/lib/sexplib0 -I /home/opam/.opam/4.12/lib/spawn -I /home/opam/.opam/4.12/lib/splittable_random -I /home/opam/.opam/4.12/lib/stdio -I /home/opam/.opam/4.12/lib/stdlib-shims -I /home/opam/.opam/4.12/lib/time_now -I /home/opam/.opam/4.12/lib/timezone -I /home/opam/.opam/4.12/lib/typerep -I /home/opam/.opam/4.12/lib/uchar -I /home/opam/.opam/4.12/lib/uutf -I /home/opam/.opam/4.12/lib/variantslib -I src/common/.common_eml.objs/byte -intf-suffix .ml -no-alias-deps -o src/.ppx_eml.objs/byte/ppx_eml.cmo -c -impl src/ppx_eml.ml)
# File "src/ppx_eml.ml", line 16, characters 6-29:
# 16 |       Parser.parse_expression Lexer.token buffer
#            ^^^^^^^^^^^^^^^^^^^^^^^
# Alert deprecated: module Ppxlib.Parser
# Accessing this module directly is deprecated, use Ocaml_common.Parser instead
# File "src/ppx_eml.ml", line 16, characters 6-29:
# 16 |       Parser.parse_expression Lexer.token buffer
#            ^^^^^^^^^^^^^^^^^^^^^^^
# Error: Unbound value Parser.parse_expression
#     ocamlopt src/.ppx_eml.objs/native/ppx_eml.{cmx,o} (exit 2)
# (cd _build/default && /home/opam/.opam/4.12/bin/ocamlopt.opt -w -40 -g -I src/.ppx_eml.objs/byte -I src/.ppx_eml.objs/native -I /home/opam/.opam/4.12/lib/base -I /home/opam/.opam/4.12/lib/base/base_internalhash_types -I /home/opam/.opam/4.12/lib/base/caml -I /home/opam/.opam/4.12/lib/base/md5 -I /home/opam/.opam/4.12/lib/base/shadow_stdlib -I /home/opam/.opam/4.12/lib/base_bigstring -I /home/opam/.opam/4.12/lib/base_quickcheck -I /home/opam/.opam/4.12/lib/bin_prot -I /home/opam/.opam/4.12/lib/bin_prot/shape -I /home/opam/.opam/4.12/lib/bytes -I /home/opam/.opam/4.12/lib/containers -I /home/opam/.opam/4.12/lib/containers/monomorphic -I /home/opam/.opam/4.12/lib/core -I /home/opam/.opam/4.12/lib/core/error_checking_mutex -I /home/opam/.opam/4.12/lib/core_kernel -I /home/opam/.opam/4.12/lib/core_kernel/base_for_tests -I /home/opam/.opam/4.12/lib/core_kernel/caml_unix -I /home/opam/.opam/4.12/lib/core_kernel/flags -I /home/opam/.opam/4.12/lib/core_kernel/version_util -I /home/opam/.opam/4.12/lib/fieldslib -I /home/opam/.opam/4.12/lib/gen -I /home/opam/.opam/4.12/lib/jane-street-headers -I /home/opam/.opam/4.12/lib/menhirLib -I /home/opam/.opam/4.12/lib/ocaml-compiler-libs/common -I /home/opam/.opam/4.12/lib/ocaml-compiler-libs/shadow -I /home/opam/.opam/4.12/lib/ocaml/compiler-libs -I /home/opam/.opam/4.12/lib/ocaml/threads -I /home/opam/.opam/4.12/lib/parsexp -I /home/opam/.opam/4.12/lib/ppx_assert/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_bench/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_compare/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_derivers -I /home/opam/.opam/4.12/lib/ppx_enumerate/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_expect/collector -I /home/opam/.opam/4.12/lib/ppx_expect/common -I /home/opam/.opam/4.12/lib/ppx_expect/config -I /home/opam/.opam/4.12/lib/ppx_expect/config_types -I /home/opam/.opam/4.12/lib/ppx_hash/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_here/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_inline_test/config -I /home/opam/.opam/4.12/lib/ppx_inline_test/runtime-lib -I /home/opam/.opam/4.12/lib/ppx_module_timer/runtime -I /home/opam/.opam/4.12/lib/ppx_sexp_conv/runtime-lib -I /home/opam/.opam/4.12/lib/ppxlib -I /home/opam/.opam/4.12/lib/ppxlib/ast -I /home/opam/.opam/4.12/lib/ppxlib/astlib -I /home/opam/.opam/4.12/lib/ppxlib/print_diff -I /home/opam/.opam/4.12/lib/ppxlib/stdppx -I /home/opam/.opam/4.12/lib/ppxlib/traverse_builtins -I /home/opam/.opam/4.12/lib/sedlex -I /home/opam/.opam/4.12/lib/seq -I /home/opam/.opam/4.12/lib/sexplib -I /home/opam/.opam/4.12/lib/sexplib/unix -I /home/opam/.opam/4.12/lib/sexplib0 -I /home/opam/.opam/4.12/lib/spawn -I /home/opam/.opam/4.12/lib/splittable_random -I /home/opam/.opam/4.12/lib/stdio -I /home/opam/.opam/4.12/lib/stdlib-shims -I /home/opam/.opam/4.12/lib/time_now -I /home/opam/.opam/4.12/lib/timezone -I /home/opam/.opam/4.12/lib/typerep -I /home/opam/.opam/4.12/lib/uchar -I /home/opam/.opam/4.12/lib/uutf -I /home/opam/.opam/4.12/lib/variantslib -I src/common/.common_eml.objs/byte -I src/common/.common_eml.objs/native -intf-suffix .ml -no-alias-deps -o src/.ppx_eml.objs/native/ppx_eml.cmx -c -impl src/ppx_eml.ml)
# File "src/ppx_eml.ml", line 16, characters 6-29:
# 16 |       Parser.parse_expression Lexer.token buffer
#            ^^^^^^^^^^^^^^^^^^^^^^^
# Alert deprecated: module Ppxlib.Parser
# Accessing this module directly is deprecated, use Ocaml_common.Parser instead
# File "src/ppx_eml.ml", line 16, characters 6-29:
# 16 |       Parser.parse_expression Lexer.token buffer
#            ^^^^^^^^^^^^^^^^^^^^^^^
# Error: Unbound value Parser.parse_expression

Also 0.4 and 0.5.1 fail in the same way. Seen on https://opam.ci.ocaml.org/github/ocaml/opam-repository/commit/a3c26463383f3d7040dc6c9eff36c7e4d433751e