Another edge case revert

Author: rbell517

nisystemlink/clients/tag/_tag_subscription.py

@@ -46,7 +46,7 @@ def my_callback(tag: TagData, reader: TagValueReader | None):
     # Under certain circumstances, mypy complains about the event not having a type hint
     # unless we specify it explicitly. (But we also need to delete the attribute so that
     # Events.__getattr__ can do its magic.)
-    tag_changed: events._EventSlot = None  # type: ignore[assignment]
+    tag_changed = None  # type: events._EventSlot
     del tag_changed
 
     _HEARTBEAT_INTERVAL_MILLISECONDS = 30000.0