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

Tempest 21.0.0 is released now, which marks the end of support
for Pike release - https://review.opendev.org/#/c/670700/

We do not need to run the Pike stable job om master gate now.
Depends-On: https://review.opendev.org/#/c/670700/

Change-Id: I7db428c02bbe3ae8ecdc3679817cb20b7a8a63dd

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