add sweeper for google_gke_hub_scope (#15588)

Author: shuyama1

mmv1/products/gkehub2/Scope.yaml

@@ -47,9 +47,6 @@ iam_policy:
   import_format:
     - 'projects/{{project}}/locations/global/scopes/{{scope_id}}'
     - '{{scope_id}}'
-custom_code:
-# Skip sweeper gen since this is a child resource.
-exclude_sweeper: true
 examples:
   - name: 'gkehub_scope_basic'
     primary_resource_id: 'scope'