repo group: drop pointless double handling of parent_group_id updates

kallithea/model/repo_group.py

@@ -284,9 +284,6 b' class RepoGroupModel(object):'
             if 'group_description' in repo_group_args:
                 repo_group.group_description = repo_group_args['group_description']
             if 'parent_group_id' in repo_group_args:
-                repo_group.parent_group_id = repo_group_args['parent_group_id']
-
-            if 'parent_group_id' in repo_group_args:
                 assert repo_group_args['parent_group_id'] != '-1', repo_group_args  # RepoGroupForm should have converted to None
                 repo_group.parent_group = db.RepoGroup.get(repo_group_args['parent_group_id'])
             if 'group_name' in repo_group_args: