Remove release-openstack-server template
Remove release-openstack-server template

Once nothing uses it anymore, we don't need the template.

Depends-On: https://review.openstack.org/598323
Depends-On: https://review.openstack.org/606079
Depends-On: https://review.openstack.org/606073
Change-Id: I77d2ed3a3f1718b22e751aba113c2a3deb36f315

openstack-infra/openstack-zuul-jobs,openstack-infra/openstack-zuul-jobs