Temporarily revert git panel diff editor feature (#22733)

The existing code was causing us to constantly re-scan files when
anything changed in the project. Temporarily revert this as we're about
to rework this entire UI with the new primitives.

follow up to https://github.com/zed-industries/zed/pull/22329

Release Notes:

- N/A

---------

Co-authored-by: Cole <cole@zed.dev>

crates/project/src/project.rs

@@ -244,7 +244,6 @@ pub enum Event {
     ActivateProjectPanel,
     WorktreeAdded(WorktreeId),
     WorktreeOrderChanged,
-    GitRepositoryUpdated,
     WorktreeRemoved(WorktreeId),
     WorktreeUpdatedEntries(WorktreeId, UpdatedEntriesSet),
     WorktreeUpdatedGitRepositories(WorktreeId),
@@ -2307,7 +2306,6 @@ impl Project {
             }
             WorktreeStoreEvent::WorktreeOrderChanged => cx.emit(Event::WorktreeOrderChanged),
             WorktreeStoreEvent::WorktreeUpdateSent(_) => {}
-            WorktreeStoreEvent::GitRepositoryUpdated => cx.emit(Event::GitRepositoryUpdated),
         }
     }