chore: Remove unused Optional import

Co-Authored-By: mkeeler@launchdarkly.com <keelerm84@gmail.com>

Author: devin-ai-integration[bot]

contract-tests/flag_change_listener.py

@@ -1,6 +1,6 @@
 import logging
 import threading
-from typing import Callable, Dict, Optional
+from typing import Callable, Dict
 
 import requests