Remove mox3 in test-requirement.txt
Remove mox3 in test-requirement.txt

mox3 was used for unit tests. But now we replace it with mock.
So I think there no need to keep it in test-requirement.txt.

Change-Id: Id2179d6611d95939b359d62942e4b4e3f64e1715

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