Remove the stable rocky from supported branch in Tempest master

Rocky is in Extended Maintainance state now so we can
remove this from supported branch and also remove its
jobs to run on master gate.

-https://releases.openstack.org/

Depends-On: https://review.opendev.org/#/c/722186/

Change-Id: I46f4abf07839fb5e8767635e2502e97e8409b8b8
2 files changed