Fix warnings when `mix test` is executed

[kentaro]

mix test generates the warnings below:

$ mix test
Compiling 4 files (.ex)
warning: variable "definitions" is unused (if the variable is not meant to be used, prefix it with an underscore)
  lib/neotomex/grammar.ex:353: Neotomex.Grammar.match/3

warning: variable "expr_trans" is unused (if the variable is not meant to be used, prefix it with an underscore)
  lib/neotomex/grammar.ex:352: Neotomex.Grammar.match/3

warning: this clause cannot match because a previous clause at line 308 always matches
  lib/neotomex/grammar.ex:314

warning: Dbg.clear/0 is undefined (module Dbg is not available or is yet to be defined)
  lib/neotomex.ex:34: Neotomex.clear_trace/0

warning: Dbg.local_call/1 is undefined (module Dbg is not available or is yet to be defined)
  lib/neotomex.ex:25: Neotomex.trace/0

warning: Dbg.trace/2 is undefined (module Dbg is not available or is yet to be defined)
  lib/neotomex.ex:23: Neotomex.trace/0

Generated neotomex app
..............................

Finished in 0.2 seconds (0.00s async, 0.2s sync)
3 doctests, 27 tests, 0 failures

Randomized with seed 752248

To suppress these warnings, I fix the code along with these warnings messages, in addition to updating dependencies.

This fix doesn't break any tests.