[clang] [Clang] Use getNonTypeTemplateArgumentType fallback in getTypeOfConstantTemplateParameter (PR #231983)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

> I'd very much like to have tests for that but i can't really come up with one, and i don't want us to leave the codebase as-is so, unless someone has an idea how to test that change in the next day or 2, LGTM

Don't the tests in the previous PR cover this?

https://github.com/llvm/llvm-project/pull/231983