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

[Louis Dionne via llvm-commits]

ldionne wrote:

Hmm, I just saw your post here: https://discourse.llvm.org/t/changes-to-pull-request-subscription-system/73296/15.

I am fine with abandoning this PR in favour of fixing the CODEOWNERS file as a whole, but I'd like to get this fixed sooner rather than later so we can be back in a state of parity with Phabricator for the runtimes.

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