text: Title: [GCP] Fail to terminate CPU instances when MIG configuration is set
  Body: To reproduce:
  1. `export SKYPILOT_CONFIG=tests/test_yamls/use_mig_config.yaml`
  ```
  managed_instance_group:
      run_duration: 30
      provision_timeout: 600
  ```
  3. `sky launch -c mig-down --cloud gcp --cpus 2 echo hi`
  4. `sky down mig-down`
  ```
    File "/opt/conda/envs/sky-oss/lib/python3.10/site-packages/googleapiclient/http.py", line 938, in execute
      raise HttpError(resp, content, uri=self.uri)
  googleapiclient.errors.HttpError: <HttpError 403 when requesting https://compute.googleapis.com/compute/beta/projects/sky-dev-465/zones/us-central1-a/instanceGroupManagers/sky-mig-mig-down-11d9/resizeRequests?filter=state+eq+ACCEPTED&alt=json returned "Required 'compute.instanceGroupManagers.get' permission for 'projects/sky-dev-465/zones/us-central1-a/instanceGroupManagers/sky-mig-mig-down-11d9'". Details: "[{'message': "Required 'compute.instanceGroupManagers.get' permission for 'projects/sky-dev-465/zones/us-central1-a/instanceGroupManagers/sky-mig-mig-down-11d9'", 'domain': 'global', 'reason': 'forbidden'}]">
  ```