[trove] 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: I9d640eb5e6901c32b5a7b7e1b12e23f61cd1ca50

deliverables/xena/python-troveclient.yaml

@@ -15,6 +15,10 @@ releases:
     projects:
       - repo: openstack/python-troveclient
         hash: 64f3f62368e3f278ce235d1cd22bc3b280d1f860
+  - version: xena-em
+    projects:
+      - repo: openstack/python-troveclient
+        hash: 64f3f62368e3f278ce235d1cd22bc3b280d1f860
 branches:
   - name: stable/xena
     location: 7.1.1