Make neutron-tempest-plugin-designate-scenario voting

As this job looks very stable since quite long time, we decided
on Neutron CI meeting to promote it to be voting in check queue.

Change-Id: Ibfd35f6a5ba37f62590a0208dc74c4cee7d23b0a
diff --git a/.zuul.yaml b/.zuul.yaml
index a854586..adcb433 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -187,7 +187,6 @@
       - ^(test-|)requirements.txt$
       - ^releasenotes/.*$
       - ^setup.cfg$
-    voting: false
 
 - job:
     name: neutron-tempest-plugin-designate-scenario-queens