[clang] [clang][Sema] Improve template argument deduction diagnostic (PR #122754)

[Vlad Serebrennikov via cfe-commits]

https://github.com/Endilll commented:

The way you applied changes to C++ DR tests is good, but I think the diagnostic message would benefit from further wordsmithing.

https://github.com/llvm/llvm-project/pull/122754