remove unused code

Author: bdraco

onvif/client.py

@@ -547,6 +547,7 @@ async def create_notification_manager(
     async def close(self) -> None:
         """Close all transports."""
         await self._snapshot_client.close()
+        await self._snapshot_connector.close()
         for service in self.services.values():
             await service.close()