[clang] [clang] Fix mangling of constrained auto referring to a parameter when the return type has an ABI tag (PR #223121)

[Corentin Jabot via cfe-commits]

https://github.com/cor3ntin approved this pull request.

LGTM. Do you need us to merge that for you?

https://github.com/llvm/llvm-project/pull/223121