[clang] [clang] Warn about deprecated volatile-qualified return types (PR #137899)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

> @shafik I have changed the commit message, can you please look again?

I see the commit [238d737](https://github.com/llvm/llvm-project/pull/137899/commits/238d73776c85ed22386ac494f275261638cd40d3) which adds the improved summary but I don't see at the top of this page in the summary. As long as this is what ends up as the commit message that is fine but it is better to just edit the summary at the top of the page so the reviewers can see it up front. Thank you!

https://github.com/llvm/llvm-project/pull/137899