[swift] Unmaintained branch cleanup

Swift currently has six unmaintained branches: - unmaintained/2023.1 - unmaintained/zed - unmaintained/yoga - unmaintained/xena - unmaintained/wallaby - unmaintained/victoria Half of them have not been updated this year. For all of them, the only patches since the transition to unmaintained status were to try to maintain CI. While two of them have open patches, they all seem to revolve around maintaining CI and none of them currently pass. I propose transitioning all of these to end-of-life. If you have any objections, please respond here on the mailing list or at https://review.opendev.org/c/openstack/releases/+/958101 which makes the change. Tim