[clang] [Clang] Fix inverted diagnostic location for duplicate default labels (PR #180447)

[Thibault Monnier via cfe-commits]

https://github.com/Thibault-Monnier requested changes to this pull request.

Please clean this up. You might want to look at https://discourse.llvm.org/t/rfc-llvm-ai-tool-policy-human-in-the-loop/89159/26.

https://github.com/llvm/llvm-project/pull/180447