Re-enable upgrade job

Now that we've pinned the kafka library, we can re-enable the
upgrade job.

Change-Id: I60b16ad94c6e7565dcf0aaf683fefedebc709b0d

.zuul.yaml

@@ -391,7 +391,7 @@
         - zuul-nox-py311
         - zuul-nox-py311-multi-scheduler
         - zuul-nox-py312
-        # - zuul-nox-upgrade
+        - zuul-nox-upgrade
         - zuul-build-dashboard-openstack-whitelabel
         - zuul-build-dashboard-software-factory
         - zuul-build-dashboard-opendev
@@ -423,7 +423,7 @@
             nodeset: ubuntu-jammy
         - zuul-nox-py311
         - zuul-nox-py312
-        # - zuul-nox-upgrade
+        - zuul-nox-upgrade
         - zuul-build-dashboard
         - nodejs-run-lint:
             vars: