Rollup merge of #147354 - chenyukang:yukang-fix-147070-wrong-highlight-span, r=estebank

Fix wrong span for hightlight for duplicated diff lines

Fixes rust-lang/rust#147070

From comments: rust-lang/rust#147070 (comment)
The lightlight row for diff must at least 2.

r? `@estebank`

Author: matthiaskrgr