[clang-tools-extra] [include-cleaner] don't consider the associated header unused (PR #67228)

[Mike Weller via cfe-commits]

MikeWeller wrote:

Is it @sam-mccall who needs to address remaining comments? Or how can we move this along? I'd also be keen on getting this change merged.

https://github.com/llvm/llvm-project/pull/67228