Previously this was guarded with macros that are defined by <bit> itself.

Note that libc++ also had a bug that was fixed last week
https://github.com/llvm/llvm-project/commit/a4f0764aefd6ea41e83a5974f582a1a7e985667d

PiperOrigin-RevId: 543511181
Change-Id: I1b8efa32f721ad450f8d1803c6c6c8373ad0371c