git_ui: Fix commit modal buttons hidden at small ui_font_size (#56366)

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
- [ ] Performance impact has been considered and is acceptable

Closes #55939.

Release Notes:

- Fixed commit modal buttons being hidden for `ui_font_size` values

crates/git_ui/src/commit_modal.rs

@@ -622,7 +622,7 @@ impl Render for CommitModal {
                 }),
             )
             .w(width)
-            .h_112()
+            .min_h_112()
             .p(container_padding)
             .elevation_3(cx)
             .overflow_hidden()