`name` field of `TypeName` is const on 1.8

[KristofferC]

Just a heads up of a change in the internals in Julia for 1.8 that causes a breakage of this package:

valid: Error During Test at /home/pkgeval/.julia/packages/RedefStructs/JMYNd/test/runtests.jl:7
  Test threw exception
  Expression: begin
    #= /home/pkgeval/.julia/packages/RedefStructs/JMYNd/test/runtests.jl:7 =# @redef struct S
        end
    true
end
  setfield!: const field .name of type TypeName cannot be changed
  Stacktrace:
   [1] setproperty!(x::Core.TypeName, f::Symbol, v::Symbol)
     @ Base ./Base.jl:39
   [2] macro expansion
     @ ~/.julia/packages/RedefStructs/JMYNd/src/RedefStructs.jl:45 [inlined]
   [3] macro expansion
     @ /opt/julia/share/julia/stdlib/v1.8/Test/src/Test.jl:464 [inlined]
   [4] macro expansion
     @ ~/.julia/packages/RedefStructs/JMYNd/test/runtests.jl:7 [inlined]
   [5] macro expansion

PkgEval log: https://s3.amazonaws.com/julialang-reports/nanosoldier/pkgeval/by_hash/f51f24c_vs_2ca8b0c/RedefStructs.primary.log