Fix typo in enable_unsupported_driver description
Fix typo in enable_unsupported_driver description

TrivialFix

Change-Id: Ib4727a37c37829c9bdb91233fc8764f4ac331b0f

phenoxim/cinder,cloudbase/cinder,NetApp/cinder,Datera/cinder,eharney/cinder,Hybrid-Cloud/cinder,Datera/cinder,phenoxim/cinder,openstack/cinder,NetApp/cinder,eharney/cinder,mahak/cinder,cloudbase/cinder,openstack/cinder,ge0rgi/cinder,Hybrid-Cloud/cinder,j-griffith/cinder,Nexenta/cinder,mahak/cinder,Nexenta/cinder,j-griffith/cinder