Remove grenade neutron non-voting from the gate

This commit removes the non-voting gate-grenade-dsvm-neutron job from
the list of jobs grenade gate pipeline. We shouldn't be running
non-voting jobs in the gate pipeline as it's just a waste of resources
if the jobs don't work.

Related-Bug: #1383439

Change-Id: I14b67585330efeff6c07a40292f4bcc4fd8fd332
Merge "Remove grenade neutron non-voting from the gate"