Mark centos-9-stream as n-v on stable/yoga

The devstack-platform-centos-9-stream job has been failing
on stable/yoga branch for some time now. Let's put it to n-v
to unblock the gate.

Change-Id: I2c1eadc43adfbfbb2bb377a529d7af55aba5d4ee

.zuul.yaml

@@ -650,6 +650,7 @@
     parent: tempest-full-py3
     description: CentOS 9 Stream platform test
     nodeset: devstack-single-node-centos-9-stream
+    voting: false
     timeout: 9000
     vars:
       configure_swap_size: 4096
@@ -825,7 +826,6 @@
       jobs:
         - devstack
         - devstack-ipv6
-        - devstack-platform-centos-9-stream
         - devstack-enforce-scope
         - devstack-multinode
         - devstack-unit-tests