tests: drop old unittest.main logic

We use pytest now which doesn't need this boilerplate.

Change-Id: Ib71d90b3f1669897814ee768927b5b595ca8d789
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/354355
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

tests/test_git_config.py

@@ -200,7 +200,3 @@ class GitConfigReadWriteTests(unittest.TestCase):
     for key, value in TESTS:
       self.assertEqual(sync_data[f'{git_config.SYNC_STATE_PREFIX}{key}'], value)
     self.assertTrue(sync_data[f'{git_config.SYNC_STATE_PREFIX}main.synctime'])
-
-
-if __name__ == '__main__':
-  unittest.main()