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: Idc6829c6411b5a27e44a172893276b9a26aca805

Author: openstackadmin

.zuul.d/project.yaml

@@ -1,7 +1,7 @@
 ---
 - project:
     templates:
-      - openstack-python3-wallaby-jobs
+      - openstack-python3-xena-jobs
       - check-requirements
       - publish-openstack-docs-pti
       - release-notes-jobs-python3