Mistransforms clang-tidy trailing whitespace removal instead removing the whole line

This review feedback/patch suggestion: https://github.com/carbon-language/carbon-lang/pull/5802#discussion_r2207385012 suggests removing the whole line (I think? or it's just a rendering bug?)

But the patch it's based on: https://github.com/carbon-language/carbon-lang/actions/runs/16293595698/job/46009258237?pr=5802 is only about removing the trailing whitespace.