Turn OSC tips jobs non-voting

There are several flapping tests in OSC right now - one related to
floating ips, and a set of volume tests. Turn the job to non-voting so
we don't keep blocking the ability to land things.

It's still important for SDK reviewers to look at failures here.

Change-Id: I71d2bff15e518ce7d55cd4213e85efdbf4924209

.zuul.yaml

@@ -292,7 +292,8 @@
         - openstacksdk-functional-devstack-magnum:
             voting: false
         - openstacksdk-functional-devstack-python3
-        - osc-functional-devstack-tips
+        - osc-functional-devstack-tips:
+            voting: false
         - neutron-grenade
         - openstack-tox-lower-constraints
         - nodepool-functional-py35-src
@@ -303,7 +304,6 @@
               sphinx_python: python3
         - openstacksdk-functional-devstack
         - openstacksdk-functional-devstack-python3
-        - osc-functional-devstack-tips
         - neutron-grenade
         - openstack-tox-lower-constraints
         - nodepool-functional-py35-src