Remove the Ocata stable branch jobs from master gate
Remove the Ocata stable branch jobs from master gate

Tempest 20.0.0 is released now, which marks the end of support
for Ocata release - https://review.openstack.org/#/c/645867/

We do not need to run the Ocata stable job om master gate now.
Depends-On: https://review.openstack.org/#/c/645867

Change-Id: I883f3c98201631acdadeaab6678a796a85662e44

masayukig/tempest,cisco-openstack/tempest,openstack/tempest,openstack/tempest,masayukig/tempest,cisco-openstack/tempest