Since release 1.30.0-gke.1930, the featureGates.enableGMPForSystemMetrics field in the stackdriver custom resource is always on and can't be disabled

## Breaking Since release 1.30.0-gke.1930, the `featureGates.enableGMPForSystemMetrics` field in the `stackdriver` custom resource is always on and can't be disabled. It has been enabled by default since 1.16\. If you've manually turned this feature off, upgrading clusters to version 1.30 means a breaking change in the format of some system metrics. For information on this feature, see [Use Google Cloud Managed Service for Prometheus for selected system components](https://cloud.google.com/kubernetes-engine/distributed-cloud/bare-metal/docs/how-to/log-monitoring#using-managed-service-for-prometheus).