[clang] [Clang][Sema] Fix crash when using name of UnresolvedUsingValueDecl with template arguments (PR #83842)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

Actually, I don't think the proposed fix here is quite right. If we _only_ find an `UnresolvedUsingValueDecl`, then we shouldn't assume the name is a template per [[temp.names] p3.3](http://eel.is/c++draft/temp.names#3.3)... will work on a new fix.

https://github.com/llvm/llvm-project/pull/83842