removed MagicMock from test_main.py

Author: ChaosHour

tests/test_main.py

@@ -1,6 +1,5 @@
 import unittest
 from typing import Optional  # Added by Kurt Larsen
-from unittest.mock import MagicMock
 
 from data_diff import Database, JoinDiffer, HashDiffer
 from data_diff import databases as db