Mlj.jl: MLJ_VERSION ci test fails on julia >=1.4

[OkonSamuel]

For julia version >= 1.4 MLJ_VERSION test fails see logs This is because MLJ isn't in the dependency graph while testing with julia versions >= 1.4.
We have 2 choices here

1. revert to using Pkg.Toml.parse as in

 using Pkg.TOML 
 const MLJ_VERSION =
  VersionNumber(TOML.parsefile(joinpath(dirname(@__DIR__), "Project.toml"))["version"])`

1. disable ci tests for MLJ_VERSION while testing with julia version >=1.4

@tlienart , @ablaom , @DilumAluthge

[ablaom]

Well, looks like we're going round and round with this one. 😵

Unless @DilumAluthge wants to suggest a more canonical method of doing this, I'm happy for 1. I don't understand option 2, as it removes a test for something broken, no?

[DilumAluthge]

I think parsing the Project.toml file is the best bet here.