doc: Move the note to an appropriate place
doc: Move the note to an appropriate place

"Description" field is also added to match the current version.

Change-Id: Ia05d1873d69500b9e2c576fcb8abe9dbdeba25e8
Closes-Bug: #1742327

ChameleonCloud/horizon,openstack/horizon,noironetworks/horizon,ChameleonCloud/horizon,ChameleonCloud/horizon,openstack/horizon,NeCTAR-RC/horizon,ChameleonCloud/horizon,openstack/horizon,noironetworks/horizon,noironetworks/horizon,noironetworks/horizon,NeCTAR-RC/horizon,openstack/horizon,NeCTAR-RC/horizon,NeCTAR-RC/horizon