settings: Fix missing typing import.

The world previously passed CI only because old versions of
prod_settings_template have this already present via the * import.

zproject/settings.py

@@ -14,7 +14,7 @@ from copy import deepcopy
 import os
 import time
 import sys
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, List, Tuple, Union
 from urllib.parse import urljoin
 
 from zerver.lib.db import TimeTrackingConnection