REPLCompletions: remove `builtin_tfunction(::REPLInterpreter)` overload (#58585)
This overload was necessary in the past, but in the current compiler
implementation, all `getglobal` calls that were aggressively concretized
by this overload are already concretized by `concrete_eval_call`. So
this overload is no longer necessary.
- closes JuliaLang/julia#58537