Disable voting on openSUSE

There's been issues in the past week with openSUSE image builds timing
out. This may be due to issues with openSUSE's infrastructure [0]. For
the time being, we should disable the openSUSE docker build until we are
able to consistently build without failures.

[0] https://status.opensuse.org/

Change-Id: I6f3cb9867898a3371cedc58835633ac6eb9ad99b

.zuul.yaml

@@ -70,6 +70,7 @@
 - job:
     name: spyglass-docker-build-gate-opensuse
     timeout: 1800
+    voting: false
     run: tools/gate/playbooks/docker-image-build.yaml
     nodeset: spyglass-single-node
     vars:
@@ -116,6 +117,7 @@
 - job:
     name: spyglass-docker-publish-opensuse
     timeout: 1800
+    voting: false
     run: tools/gate/playbooks/docker-image-build.yaml
     nodeset: spyglass-single-node
     secrets: