rate_limiter: Set RATE_LIMITING_RULES rules to empty in test_settings.

This makes the state cleaner for the tests. Tests that want to have rate
limiting set up their own desired rules anyway, and having some
pre-existing ones from the default settings can conflict with the
desired ones.

zproject/test_settings.py

@@ -219,3 +219,8 @@ SOCIAL_AUTH_SAML_ENABLED_IDPS = {
         "display_name": "Test IdP",
     }
 }
+
+RATE_LIMITING_RULES = {
+    'api_by_user': [],
+    'authenticate': [],
+}