[clang] [Clang][Parse] Fix assertion when annotating a failed decltype-specifier (PR #211221)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for working on this, it should come with release notes in `clang/docs/ReleaseNotes.md` so users know about the fix.

https://github.com/llvm/llvm-project/pull/211221