Gate: disable ubuntu multinode voting gate.

This PS disables the multinode ubuntu gate from voting, which has
been failing due to -infra issues - and severly hampering development
work as a result.

Change-Id: I411ebe20ba19c52475b559952712faf742343673

.zuul.yaml

@@ -45,6 +45,7 @@
               - ^doc/.*$
               - ^releasenotes/.*$
         - openstack-helm-multinode-ubuntu:
+            voting: false
             irrelevant-files:
               - ^.*\.rst$
               - ^doc/.*$
@@ -109,11 +110,6 @@
               - ^.*\.rst$
               - ^doc/.*$
               - ^releasenotes/.*$
-        - openstack-helm-multinode-ubuntu:
-            irrelevant-files:
-              - ^.*\.rst$
-              - ^doc/.*$
-              - ^releasenotes/.*$
         - openstack-helm-kolla-deploy-ceph-ovs:
             irrelevant-files:
               - ^.*\.rst$