libcxx-compat: revert llvmorg-19-init-5639-ga10aa4485e83:
[libc++] Simplify the implementation of remove_reference (#85207) GCC 13 introduced the type trait `__remove_reference`. We can simplify the implementation of `remove_reference` a bit by using it.
PR: 280562
MFC after: 1 month
(cherry picked from commit a7b2d7f261b81d141195c4204fdc4a0dc97a146e)