This PR calls 'cursor_pointer()' on the appropriate UI elements. It is a
very small change, but it is my first time contributing, so please let
me know if I have made any mistakes.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #55218

Release Notes:

- Fixed the mouse cursor not switching to cursor pointer when hovering
commit rows in the git graph