Fix the documentation for HIDDEN support status
Fix the documentation for HIDDEN support status

There were a few inaccuracies in the documentation for the HIDDEN
support status.

Change-Id: I0960c5e342f01035834ce82520eb64e5ded84c6a

openstack/heat,noironetworks/heat,openstack/heat,steveb/heat,steveb/heat,noironetworks/heat,cwolferh/heat-scratch,cwolferh/heat-scratch