Posture check: GCP Vertex AI Workbench user-managed notebook's JupyterLab interface access mode is set to single user
Query: ```config from cloud.resource where cloud.type = 'gcp' AND api.name = 'gcloud-vertex-ai-notebook-instance' AND json.rule = state equals "ACTIVE" and ( metadata.proxy-mode equals "mail" or metadata.proxy-user-mail exists )```