Import unittest.mock explicitly in test_tsg_parser

Co-authored-by: tausbn <1104778+tausbn@users.noreply.github.com>

Author: Copilot

python/extractor/tests/test_tsg_parser.py

@@ -1,4 +1,5 @@
 import unittest
+import unittest.mock
 import json
 
 from semmle.logging import format_message