Use Optional not X | None

src/dvc_data/index/diff.py

@@ -264,7 +264,7 @@ def _get_key(change):
     deleted.sort(key=_get_key)
 
     # Create a dictionary for fast lookup of deletions by hash_info
-    deleted_dict: dict[HashInfo | None, deque[Change]] = defaultdict(deque)
+    deleted_dict: dict[Optional[HashInfo], deque[Change]] = defaultdict(deque)
     for change in deleted:
         # We checked change.old for all deleted above, so cast
         change_hash = cast(DataIndexEntry, change.old).hash_info