Fix inline diagnostics in the project diff (#26275)

https://github.com/zed-industries/zed/blob/205f9a9f0391da47a87cac45a41f67d2a23f5a95/crates/editor/src/element.rs#L1643

Due to the snippet above, Zed is supposed to have `row` larger or equal
to `start_row` here:


https://github.com/zed-industries/zed/blob/205f9a9f0391da47a87cac45a41f67d2a23f5a95/crates/editor/src/element.rs#L1694

yet the panic were reported when clicking in the project diff.

That project diff has a lot of highlighting happening already, so the PR
disables inline diagnostics within a git diff view.


Release Notes:

- N/A

crates/git_ui/src/project_diff.rs

@@ -138,6 +138,7 @@ impl ProjectDiff {
                 window,
                 cx,
             );
+            diff_display_editor.disable_inline_diagnostics();
             diff_display_editor.set_expand_all_diff_hunks(cx);
             diff_display_editor.register_addon(GitPanelAddon {
                 workspace: workspace.downgrade(),