api: Remove spammy json_success content for edit_user_group.

These values were unnecessary translated strings not displayed
anywhere, and were not consistent with Zulip's API standards.

zerver/openapi/zulip.yaml

@@ -2288,10 +2288,8 @@ paths:
                 - $ref: '#/components/schemas/JsonSuccess'
                 - example:
                       {
-                          "description": "Description successfully updated.",
                           "result": "success",
-                          "msg": "",
-                          "name": "Name successfully updated."
+                          "msg": ""
                       }
 
         '400':

zerver/tests/test_user_groups.py

@@ -152,8 +152,6 @@ class UserGroupAPITestCase(ZulipTestCase):
         }
         result = self.client_patch('/json/user_groups/{}'.format(user_group.id), info=params)
         self.assert_json_success(result)
-        self.assertEqual(result.json()['name'], 'Name successfully updated.')
-        self.assertEqual(result.json()['description'], 'Description successfully updated.')
 
         # Test when new data is not supplied.
         result = self.client_patch('/json/user_groups/{}'.format(user_group.id), info={})
@@ -185,7 +183,6 @@ class UserGroupAPITestCase(ZulipTestCase):
         }
         result = self.client_patch('/json/user_groups/{}'.format(user_group.id), info=params)
         self.assert_json_success(result)
-        self.assertEqual(result.json()['description'], 'Description successfully updated.')
 
     def test_user_group_update_by_guest_user(self) -> None:
         hamlet = self.example_user('hamlet')

zerver/views/user_groups.py

@@ -44,16 +44,13 @@ def edit_user_group(request: HttpRequest, user_profile: UserProfile,
 
     user_group = access_user_group_by_id(user_group_id, user_profile)
 
-    result = {}
     if name != user_group.name:
         do_update_user_group_name(user_group, name)
-        result['name'] = _("Name successfully updated.")
 
     if description != user_group.description:
         do_update_user_group_description(user_group, description)
-        result['description'] = _("Description successfully updated.")
 
-    return json_success(result)
+    return json_success()
 
 @require_member_or_admin
 @has_request_variables