Remove mox3 from test-requirements.txt
Remove mox3 from test-requirements.txt

Change-Id: I9719d9b308811e7bf218af2f7da949b6c0509fc1
Closes-Bug: #1753504

openstack/python-neutronclient,noironetworks/python-neutronclient,openstack/python-neutronclient,noironetworks/python-neutronclient