Properly calculate expanded git diff hunk highlight ranges (#11632)

Closes https://github.com/zed-industries/zed/issues/11576

Release Notes:

- Fixed expanded diff hunks highlighting an extra row as added
([11576](https://github.com/zed-industries/zed/issues/11576))
4762e52d31Kirill Bulatov committed on 5/9/2024, 11:02:56 PM· committed by GitHubparent50c45c7
7 files changedLine totals unavailable