[clang] [clang-format] Fix annotating attrs in class/struct (PR #124634)

[Gedare Bloom via cfe-commits]

gedare wrote:

> I'd add an annotating test. (And drop the formatting test.)

Yes, that's a good idea, I've done it. I started with the formatting test, but it is unnecessary (although a good, complicated bit of formatting) since the bug was in the annotation.

https://github.com/llvm/llvm-project/pull/124634