[llvm] [Sema] Use underlying type of scoped enum for -Wformat diagnostics (PR #67378)

[Shoaib Meenai via llvm-commits]

smeenai wrote:

I updated the release notes. I was planning to ask for a pick into 17, but I'll just tweak the release notes for the pick and modify the Clang 18 release notes afterwards if it's accepted.

https://github.com/llvm/llvm-project/pull/67378