Fix "Project Diff Opened" event name (#24686)

Release Notes:

- N/A

crates/git_ui/src/project_diff.rs

@@ -407,7 +407,7 @@ impl Item for ProjectDiff {
     }
 
     fn telemetry_event_text(&self) -> Option<&'static str> {
-        Some("project diagnostics")
+        Some("Project Diff Opened")
     }
 
     fn as_searchable(&self, _: &Entity<Self>) -> Option<Box<dyn SearchableItemHandle>> {