[clang] [Clang][Parser] Don't always destroy template annotations at the end of a declaration (PR #89494)

[Younan Zhang via cfe-commits]

zyn0217 wrote:

> Are there actually any benefit from being that eager to delete template annotations?

Well, I don't have much context of that patch, but I think that makes sense in part e.g. When we have a function that involves many generic lambdas, where we would destroy template annotations at the end of each lambda, comparing to destroying these at the end of the function.

https://github.com/llvm/llvm-project/pull/89494