Cleanup publish-openstack-releasenotes jobs
Cleanup publish-openstack-releasenotes jobs

Remove publish-openstack-releasenotes job, it's not used.

Now we don't need publish-openstack-releasenotes-base anymore, so merge
publish-openstack-releasenotes-python3 and it's parent.

Depends-On: https://review.opendev.org/685598
Depends-On: https://review.opendev.org/685599
Depends-On: https://review.opendev.org/685600
Change-Id: I46d724c2a2aa63902022101686e6972cbd01e76c

openstack-infra/project-config,openstack-infra/project-config