Update manila-grenade-skip-level job for new release
Update manila-grenade-skip-level job for new release

2023.1 is SLURP release and can test the upgrade from
stable/yoga to 2023.1 by manila-grenade-skip-level job.

This commit updates the setting for that job to do so and
also add branches variant to avoid running it on non-SLURP
(zed) release gate.

Change-Id: I0381d89ee7a3c6974ad3b2e1853a4c1ef4b4e77c

openstack/manila,openstack/manila