[OpenStackAnsible] Transition Xena to EM

This transition the stable/xena branch to extended maintenance.
Changes for bugfixes and things the team deems important are
still encouraged, but there will no longer be official releases
off of the branch after the transition.

Please +1 if the team is ready for us to proceed with this
transition, or -1 if there are any final backports currently in
flight that we should wait for. For the latter case, please
update the patch with the new commit hash after doing a final
release to get those changes out so we know to proceed with the
transition.

The transition deadline is April 20th, 2023.

Change-Id: I19f8a71535019cd1371b6fbdd94ab9c5d99e9fd2

deliverables/xena/openstack-ansible.yaml

@@ -72,6 +72,10 @@ releases:
     projects:
       - repo: openstack/openstack-ansible
         hash: e1522c27907c6aa6dbe68a831791cd45fb01dac4
+  - version: xena-em
+    projects:
+      - repo: openstack/openstack-ansible
+        hash: e1522c27907c6aa6dbe68a831791cd45fb01dac4
 branches:
   - name: stable/xena
     location: 24.0.0.0rc1