[clang] [AST] Only dump desugared type when visibly different (PR #65214)

[Richard Smith via cfe-commits]

https://github.com/zygoloid commented:

The change looks good and like a nice improvement to me. I don't think this is undoing any of the intended functional changes of @mizvekov's work.

https://github.com/llvm/llvm-project/pull/65214