[neutron][neutron-vpnaas] retiring train/ussuri/victoria branches

Hi everyone, At the moment, the VPNaaS team is a bit low on people and in order to be able to handle the workload, I'd like to opt to only keeping maintained releases active. I propose retiring those branches unless someone steps up to fix and clean them up: https://review.opendev.org/c/openstack/releases/+/843167 Please respond to this email if you are running those releases and you are willing to maintain those older branches. Thanks Mohammed -- Mohammed Naser VEXXHOST, Inc.