tests: Fix linting issues in test_do_api_query.py

Author: shawntru04

zulip/tests/test_do_api_query.py

@@ -1,5 +1,6 @@
 import unittest
-from unittest.mock import MagicMock, patch, call
+from unittest.mock import MagicMock, patch
+
 import requests
 import zulip
 
@@ -40,8 +41,6 @@ def test_stale_connection_resets_session(self) -> None:
         fresh_session = MagicMock()
         fresh_session.request.return_value = success_response
 
-        original_ensure_session = zulip.Client.ensure_session
-
         call_count = 0
 
         def mock_ensure_session(self: zulip.Client) -> None: