Revise cluster management task

After removing the sections of the page that are not in line with the
content guide, there is little left.

Edit pages that link to removed task to no longer link there.
Redirect using 302 status so that there is a future opportunity to reinstate
the page or something like it.

- Avoid links to removed cluster management task
- Broaden applicability of “Safely Drain A Node”
- Add (stub) cluster upgrade task page
- Add a basic page about upgrading your cluster.
- Add a task page about enabling or disabling HTTP APIs

content/en/docs/concepts/configuration/pod-priority-preemption.md

@@ -321,9 +321,7 @@ Pod may be created that fits on the same Node. In this case, the scheduler will
 schedule the higher priority Pod instead of the preemptor.
 
 This is expected behavior: the Pod with the higher priority should take the place
-of a Pod with a lower priority. Other controller actions, such as
-[cluster autoscaling](/docs/tasks/administer-cluster/cluster-management/#cluster-autoscaling),
-may eventually provide capacity to schedule the pending Pods.
+of a Pod with a lower priority.
 
 ### Higher priority Pods are preempted before lower priority pods