Make freezer-web-ui-ubuntu as voting job again

freezer-web-ui-ubuntu job has been made n-v in legacy
job migration work.
- https://review.openstack.org/#/c/642610

Not issue has been fixed and it is working fine
- https://review.openstack.org/#/c/643213/3

Let's reenable it as voting.

Change-Id: I735e0dacb035770be814ca1b829c56ef9ba644ff

.zuul.yaml

@@ -7,9 +7,7 @@
       - openstack-python36-jobs
     check:
       jobs:
-        # making n-v till story#2005227
-        - freezer-web-ui-ubuntu:
-            voting: false
+        - freezer-web-ui-ubuntu
         - openstack-tox-pylint
     gate:
       jobs: