tests: setUp overrides should call super().setUp().

MigrationsTestCase is intentionally omitted from this, since migrations
tests are different in their nature and so whatever setUp()
ZulipTestCase may do in the future, MigrationsTestCase may not
necessarily want to replicate.

zerver/tests/test_hotspots.py

@@ -11,6 +11,7 @@ import ujson
 # complicated hotspots logic.
 class TestGetNextHotspots(ZulipTestCase):
     def setUp(self) -> None:
+        super().setUp()
         self.user = do_create_user(
             'user@zulip.com', 'password', get_realm('zulip'), 'user', 'user')