Fix GKE front matter, bad field docs (GoogleCloudPlatform#10018)

* Fix GKE front matter, bad field docs

* Update container_cluster.html.markdown

Author: rileykarson

mmv1/third_party/terraform/website/docs/r/container_cluster.html.markdown

@@ -6,22 +6,21 @@ description: |-
 
 # google\_container\_cluster
 
--> Visit the [Provision a GKE Cluster (Google Cloud)](https://learn.hashicorp.com/tutorials/terraform/gke?in=terraform/kubernetes&utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) Learn tutorial to learn how to provision and interact
-with a GKE cluster.
+Manages a Google Kubernetes Engine (GKE) cluster.
 
--> See the [Using GKE with Terraform](/docs/providers/google/guides/using_gke_with_terraform.html)
-guide for more information about using GKE with Terraform.
+To get more information about GKE clusters, see:
+  * [The API reference](https://cloud.google.com/kubernetes-engine/docs/reference/rest/v1beta1/projects.locations.clusters)
+  * How-to guides
+    * [GKE overview](https://cloud.google.com/kubernetes-engine/docs/concepts/kubernetes-engine-overview)
+    * [About cluster configuration choices](https://cloud.google.com/kubernetes-engine/docs/concepts/types-of-clusters)
+  * Terraform guidance
+    * [Using GKE with Terraform](/docs/providers/google/guides/using_gke_with_terraform.html)
+    * [Provision a GKE Cluster (Google Cloud) Learn tutorial](https://learn.hashicorp.com/tutorials/terraform/gke?in=terraform/kubernetes&utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) 
 
-Manages a Google Kubernetes Engine (GKE) cluster. For more information see
-[the official documentation](https://cloud.google.com/container-engine/docs/clusters)
-and [the API reference](https://cloud.google.com/kubernetes-engine/docs/reference/rest/v1beta1/projects.locations.clusters).
+-> On version 5.0.0+ of the provider, you must explicitly set `deletion_protection = false`
+and run `terraform apply` to write the field to state in order to destroy a cluster.
 
--> **Note**: On version 5.0.0+ of the provider, you must explicitly set `deletion_protection=false`
-(and run `terraform apply` to write the field to state) in order to destroy a cluster.
-It is recommended to not set this field (or set it to true) until you're ready to destroy.
-
-~> **Warning:** All arguments and attributes, including basic auth username and
-passwords as well as certificate outputs will be stored in the raw state as
+~> All arguments and attributes (including certificate outputs) will be stored in the raw state as
 plaintext. [Read more about sensitive data in state](https://www.terraform.io/language/state/sensitive-data).
 
 ## Example Usage - with a separately managed node pool (recommended)
@@ -1111,6 +1110,8 @@ subnet. See [Private Cluster Limitations](https://cloud.google.com/kubernetes-en
 for more details. This field only applies to private clusters, when
 `enable_private_nodes` is `true`.
 
+* `private_endpoint_subnetwork` - (Optional) Subnetwork in cluster's network where master's endpoint will be provisioned.
+
 * `master_global_access_config` (Optional) - Controls cluster master global
 access settings. If unset, Terraform will no longer manage this field and will
 not modify the previously-set value. Structure is [documented below](#nested_master_global_access_config).
@@ -1121,8 +1122,6 @@ In addition, the `private_cluster_config` allows access to the following read-on
 
 * `private_endpoint` - The internal IP address of this cluster's master endpoint.
 
-* `private_endpoint_subnetwork` - Subnetwork in cluster's network where master's endpoint will be provisioned.
-
 * `public_endpoint` - The external IP address of this cluster's master endpoint.
 
 !> The Google provider is unable to validate certain configurations of