[clang] [Clang] Fix IsOverload for function templates (PR #77323)

[Erich Keane via cfe-commits]

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

Seems fine to me, I don't see any reason that anything in the middle would cause a problem, so moving this is fine.  

https://github.com/llvm/llvm-project/pull/77323