Revert "Document new SCC allowEmptyDirVolumePlugin restriction."

[dgoodwin]

This reverts commit 47ab90a.

Feature was pulled and replaced with a more generic solution allowing the scc
to control arbitrary volume plugins.

[ahardin-rh]

👍

[ahardin-rh]

// revhistory
|link:../admin_guide/manage_scc.html[Managing Security Context Constraints]
|Updated to reflect that *EmptyDir* volumes are not currently disabled in OpenShift Online.
%
|link:../architecture/additional_concepts/authorization.html[Authorization]
|Updated to reflect that *EmptyDir* volumes are not currently disabled in OpenShift Online.
%
|link:../rest_api/kubernetes_v1.html[Kubernetes v1 REST API]
|Updated to reflect that *EmptyDir* volumes are not currently disabled in OpenShift Online.
%

[adellape]

@ahardin-rh I broke your revhistory above because I think we don't need to mention it since we never actually published this.