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

[Tom Stellard via llvm-commits]

tstellar wrote:

Anyone who wants to subscribe to a pull request using our current approach is going to have to be in the CODEOWNERS file, there's not really a way around that.  In order to get to the state you want, we are probably going to need 2 teams, one for reviewers, and one for subscribers.  This probably won't scale well if we need to do this throughout the whole project, but I don't think many other sub-projects have the same kind of structured code review process that would require this, so it might be OK.

The only other solution, I can think of would be to try to experiment with the [code review setings](https://github.com/orgs/llvm/teams/pr-subscribers-libcxx/edit/review_assignment) for the libcxx team.  You could enable "Auto Assignment", which will assign individual reviewers from the team rather than the whole team itself.  That would solve the problem of the confusting "On behalf of..."  messages, I think.

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