[libcxx-commits] [libcxx] [libc++] Disallow specializing `common_reference` (PR #141465)

[Louis Dionne via libcxx-commits]

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

LGTM but can you add a release note since this *may* break some code?

https://github.com/llvm/llvm-project/pull/141465