Stop running minion for Wallaby+

With the switch to ephemeral heat for the overcloud, the minion is no
longer viable. This change updates the branches to only run T->V where
the minion should work and was supported.

Related-Bug: #1938539
Change-Id: I5855de77b700124be0d0332ebe6a3f80524c521e

zuul.d/multinode-jobs.yaml

@@ -239,7 +239,7 @@
 - job:
     name: tripleo-ci-centos-8-containers-undercloud-minion
     parent: tripleo-ci-base-multinode-centos-8
-    branches: ^(?!stable/(newton|ocata|pike|queens|stein)).*$
+    branches: ^(stable/(train|ussuri|victoria)).*$
     vars:
       nodes: 1minion
       featureset: '061'