Update stable jobs on master gate

As zed is released, we should add its job on master
gate to keep branchless tempest plugins compatible
to stable branch.

Also, removing the stable/wallaby job as that is in EM
state.

Ref: Tempest plugins guide for stable branch testing:
- https://docs.openstack.org/tempest/latest/stable_branch_testing_policy.html

Change-Id: I28117a37a41ac76ba5561a285e417882c2d6a5a1

.zuul.yaml

@@ -44,9 +44,9 @@
         - keystone-dsvm-py3-functional-federation-ubuntu-focal:
             voting: false
         - keystone-dsvm-py3-functional-federation-ubuntu-focal-k2k
+        - keystone-dsvm-py3-functional-zed
         - keystone-dsvm-py3-functional-yoga
         - keystone-dsvm-py3-functional-xena
-        - keystone-dsvm-py3-functional-wallaby
         - keystone-protection-functional
     gate:
       jobs:
@@ -54,6 +54,12 @@
         - keystone-dsvm-py3-functional-federation-ubuntu-focal-k2k
         - keystone-protection-functional
 
+- job:
+    name: keystone-dsvm-py3-functional-zed
+    parent: keystone-dsvm-py3-functional
+    nodeset: openstack-single-node-focal
+    override-checkout: stable/zed
+
 - job:
     name: keystone-dsvm-py3-functional-yoga
     parent: keystone-dsvm-py3-functional
@@ -63,8 +69,3 @@
     name: keystone-dsvm-py3-functional-xena
     parent: keystone-dsvm-py3-functional
     override-checkout: stable/xena
-
-- job:
-    name: keystone-dsvm-py3-functional-wallaby
-    parent: keystone-dsvm-py3-functional
-    override-checkout: stable/wallaby