Wire up new tripleo upgrades jobs template

The depends-on adds a new upgrade jobs template which is wired up
here. Once wired up across tripleo we can remove excess content
providers with [1].

[1] https://review.opendev.org/c/openstack/tripleo-ci/+/769131
Depends-On: https://review.opendev.org/761188

Change-Id: Ia5197048994b10959e0c09165c8470c4066d46fd

zuul.d/layout.yaml

@@ -8,6 +8,7 @@
       - tripleo-standalone-scenarios-pipeline
       - openstack-python3-train-jobs
       - tripleo-standalone-multinode-ipa-pipeline
+      - tripleo-upgrades-train-pipeline
     check:
       jobs:
         - openstack-tox-pep8