Redo advice about cluster upgrades

Use one consistent phrase about the advice around upgrading a cluster.

Author: Tim Bannister

content/en/docs/tasks/administer-cluster/cluster-upgrade.md

@@ -8,6 +8,10 @@ weight: 350
 This page provides an overview of the steps you should follow to upgrade a
 Kubernetes cluster.
 
+The Kubernetes project recommends upgrading to the latest patch releases promptly, and
+to ensure that you are running a supported minor release of Kubernetes.
+Following this recommendation helps you to to stay secure.
+
 The way that you upgrade a cluster depends on how you initially deployed it
 and on any subsequent changes.
 

content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-certs.md

@@ -14,6 +14,11 @@ Client certificates generated by [kubeadm](/docs/reference/setup-tools/kubeadm/)
 This page explains how to manage certificate renewals with kubeadm. It also covers other tasks related
 to kubeadm certificate management.
 
+The Kubernetes project recommends upgrading to the latest patch releases promptly, and
+to ensure that you are running a supported minor release of Kubernetes.
+Following this recommendation helps you to to stay secure.
+
+
 ## {{% heading "prerequisites" %}}
 
 
@@ -165,10 +170,6 @@ if you don't have specific requirements on certificate renewal and perform Kuber
 upgrades regularly (less than 1 year in between each upgrade), kubeadm will take care of keeping
 your cluster up to date and reasonably secure.
 
-{{< note >}}
-It is a best practice to upgrade your cluster frequently in order to stay secure.
-{{< /note >}}
-
 If you have more complex requirements for certificate renewal, you can opt out from the default
 behavior by passing `--certificate-renewal=false` to `kubeadm upgrade apply` or to `kubeadm
 upgrade node`.

content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade.md

@@ -21,6 +21,10 @@ please refer to following pages instead:
 - [Upgrading a kubeadm cluster from {{< skew currentVersionAddMinor -4 >}} to {{< skew currentVersionAddMinor -3 >}}](https://v{{< skew currentVersionAddMinor -3 "-" >}}.docs.kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/)
 - [Upgrading a kubeadm cluster from {{< skew currentVersionAddMinor -5 >}} to {{< skew currentVersionAddMinor -4 >}}](https://v{{< skew currentVersionAddMinor -4 "-" >}}.docs.kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/)
 
+The Kubernetes project recommends upgrading to the latest patch releases promptly, and
+to ensure that you are running a supported minor release of Kubernetes.
+Following this recommendation helps you to to stay secure.
+
 The upgrade workflow at high level is the following:
 
 1. Upgrade a primary control plane node.