[libc++] Remove empty namespace std in type_traits. NFCI.

There is an empty `namespace std` in `type_traits` which was originally
used when `std::byte` was added in
c97d8aa86650ed795bf75a7dd735ecfaef3b8f55. At some point, the bitwise operators
on `std::byte` got relocated but this empty namespace was left around.
Remove it.

Reviewed By: Quuxplusone, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D111512

diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
index 7ad48d8..a8f5f22 100644 (file)
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -4175,13 +4175,4 @@ using __maybe_const = conditional_t<_Const, const _Tp, _Tp>;
 
 _LIBCPP_END_NAMESPACE_STD
 
-#if _LIBCPP_STD_VER > 14
-// std::byte
-namespace std  // purposefully not versioned
-{
-
-
-}
-#endif
-
 #endif // _LIBCPP_TYPE_TRAITS