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 have 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 [Using Managed Service for Prometheus](https://cloud.google.com/kubernetes-engine/distributed-cloud/vmware/docs/how-to/logging-and-monitoring#using-managed-service-for-prometheus).