[llvm] [libc++] Fix CODEOWNERS file for libc++ (PR #65344)

[Louis Dionne via llvm-commits]

ldionne wrote:

I think I don't understand what the purpose of the `pr-subscribers-libcxx` team is, then.

I think we have two "things" we're trying to achieve:
1. Notify people when a PR/issue is created.
2. Represent review authority over a part of the code.

We need the ability to have two different sets of people for these two things.

What do we use for (1)? Do we use automatic tagging of issues/PRs along with individual people setting a custom notification filter on the repository? Or do we use membership in a team like `pr-subscribers-libcxx`?

It seems to me like the CODEOWNERS file is meant to encode (2), not (1).

If we use tags to achieve notifications, then I believe the only problem we have right now is that `pr-subscribers-libcxx` is a poor name to represent "people who have review authority in libcxx", but other than that everything should work and we don't actually need two teams, since `pr-subscribers-libcxx` can be used to implement (2).

https://github.com/llvm/llvm-project/pull/65344