Unit tests do not need captchas.

tests/rest/test_events.py

@@ -145,6 +145,7 @@ class EventStreamPermissionsTestCase(RestTestCase):
         )
         self.ratelimiter = hs.get_ratelimiter()
         self.ratelimiter.send_message.return_value = (True, 0)
+        hs.config.enable_registration_captcha = False
 
         hs.get_handlers().federation_handler = Mock()