[clang] [Clang][Sema] Diagnose unexpanded packs in the template argument lists of function template specializations (PR #76677)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

As Corentin said, needs a release note, else LGTM.

https://github.com/llvm/llvm-project/pull/76677