Add Python3 xena unit tests

This is an automatically generated patch to ensure unit testing
is in place for all the of the tested runtimes for xena.

See also the PTI in governance [1].

[1]: https://governance.openstack.org/tc/reference/project-testing-interface.html

Change-Id: I24a4b8fd3d7c086b79875a2d0dd5f2399357d988

zuul.d/project.yaml

@@ -2,8 +2,8 @@
     templates:
       - check-requirements
       - openstack-cover-jobs
-      - openstack-python3-wallaby-jobs
+      - openstack-python3-xena-jobs
-      - openstack-python3-wallaby-jobs-arm64
+      - openstack-python3-xena-jobs-arm64
       - periodic-stable-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3