Remove horizon patch installation from README
Remove horizon patch installation from README

Removed the instructions from the README regarding installing patch
https://review.openstack.org/128133 into horizon since that change has
been merged into horizon

jcsp/manila-ui,hp-storage/manila-ui,hp-storage/manila-ui,openstack/manila-ui,jcsp/manila-ui,openstack/manila-ui,openstack/manila-ui,hp-storage/manila-ui,jcsp/manila-ui