[libcxx-commits] [libcxx] [libc++][NFC] Simplify the implementation of `__promote` (PR #81379)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

I think we should `#if` the old code as a whole for Clang 17 just to get this patch unblocked, and we can remove that "workaround" when we drop support for Clang 17. It's so easy to clean these up that I wouldn't stall this patch just for that reason.

https://github.com/llvm/llvm-project/pull/81379