Several lex/yacc files disappeared from the solution folder: lex.fs, pars.fs and others

[abelbraaksma]

I think this is caused by the changes here: https://github.com/dotnet/fsharp/pull/9877/files. However, some of these files may not have been visible before either.

Example after that PR:

Before that PR:

Same is true for the more active lex.fs and pars.fsfor F#, andpppars.fsandpplex.fs`.

A fix is underway: #9918.