Remove CentOS Stream 9 jobs

These no longer pass due to nova which removed Python 3.9 support.
We can add these jobs back once these jobs are migrated to CentOS
Stream 10.

Change-Id: I73454879ba836ec84da1e082993e061a61e90659

.zuul.yaml

@@ -110,12 +110,6 @@
     name: heat-functional
     parent: heat-functional-base
 
-- job:
-    name: heat-functional-centos-9-stream
-    parent: heat-functional-base
-    voting: false
-    nodeset: devstack-single-node-centos-9-stream
-
 - job:
     name: heat-functional-legacy
     parent: heat-functional-base
@@ -198,7 +192,6 @@
         - grenade-heat-multinode
         - heat-functional
         - heat-functional-legacy
-        - heat-functional-centos-9-stream
     gate:
       jobs:
         - grenade-heat-multinode