Add Python3 yoga unit tests

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

See also the PTI in governance [1].

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

Change-Id: I15d3240031c9d507a5c6b79e94b33e58a07c7227

zuul.d/projects.yaml

@@ -4,7 +4,7 @@
       - horizon-non-primary-django-jobs
       - horizon-nodejs14-jobs
       - openstack-lower-constraints-jobs
-      - openstack-python3-xena-jobs-horizon
+      - openstack-python3-yoga-jobs-horizon
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
     gate: