test_presence: Switch data setup from pointer to message flags.

This test is poorly written, in that it doesn't actually do any
verification of the results, but this at least is the correct
conversion of the data setup for it such that if we did verify its
results, the data we populated was relevant.

zerver/tests/test_presence.py

@@ -27,7 +27,7 @@ class ActivityTest(ZulipTestCase):
     def test_activity(self, unused_mock: mock.Mock) -> None:
         self.login('hamlet')
         client, _ = Client.objects.get_or_create(name='website')
-        query = '/json/users/me/pointer'
+        query = '/json/messages/flags'
         last_visit = timezone_now()
         count = 150
         for activity_user_profile in UserProfile.objects.all():