[llvm] [github] Add ClangIR to new-prs-labeler.yml (PR #86088)

[Nathan Lanza via llvm-commits]

lanza wrote:

> Make sure that the ClangIR team is created first before landing this so that everything works as expected.

What do you mean here by "ClangIR team is created"?

https://github.com/llvm/llvm-project/pull/86088