test_decorators: Replace the json/fetch_api_key endpoint in tests.

This endpoint is about to become an API-style route and have the legacy
decorator removed from its view. Other endpoints will be used in tests
instead of it.

zerver/tests/test_decorators.py

@@ -1078,8 +1078,10 @@ def test_authenticated_json_post_view_if_user_realm_is_deactivated(self) -> None
         do_reactivate_realm(user_profile.realm)
 
     def _do_test(self, user_email: Text) -> HttpResponse:
-        data = {"password": initial_password(user_email)}
-        return self.client_post(r'/json/fetch_api_key', data)
+        stream_name = "stream name"
+        self.common_subscribe_to_streams(user_email, [stream_name])
+        data = {"password": initial_password(user_email), "stream": stream_name}
+        return self.client_post(r'/json/subscriptions/exists', data)
 
     def _login(self, user_email: Text, user_realm: Realm, password: str=None) -> None:
         if password:
@@ -1113,7 +1115,7 @@ def test_authenticated_json_view_if_subdomain_is_invalid(self) -> None:
 
     def _do_test(self, user_email: str) -> HttpResponse:
         data = {"password": initial_password(user_email)}
-        return self.client_post(r'/json/fetch_api_key', data)
+        return self.client_post(r'/accounts/webathena_kerberos_login/', data)
 
 class TestZulipLoginRequiredDecorator(ZulipTestCase):
     def test_zulip_login_required_if_subdomain_is_invalid(self) -> None: