Remove trailing reference to nova-volume

fixes bug 1133076

as noted in the bug report, this section referred to
some content 'below' that didn't exist. Removed that text and
adjacent text to reflect that Cinder is the 'now' and the past
is long gone :)

Change-Id: I71607faace95d1d3f4a4958a5260f2862d1def72
Merge "Remove trailing reference to nova-volume"