Revert "Reapply "[Clang][Sema] Fix crash when 'this' is used in a dependent...

Revert "Reapply "[Clang][Sema] Fix crash when 'this' is used in a dependent class scope function template specialization that instantiates to a static member function (#87541)" (#88311)"

This reverts commit aa80f3ec.

See
https://github.com/llvm/llvm-project/pull/88311#issuecomment-2052291140.

There is a fix forward proposed but I am reverting this commit to fix
trunk.