Remove stable/wallaby job from master gate

stable/wallaby is in EM state. As Tempest and
plugins masters does not support EM stable branches,
QA team is pinning tempest in devstack stable/wallaby
tesitng[1]. With that we do not need to test the
stable/wallaby jobs on master gate

[1] https://review.opendev.org/c/openstack/devstack/+/871782

Change-Id: I79c6c5a676695b22135b21f8b4837f77bd2eb876

.zuul.yaml

@@ -13,8 +13,6 @@
             voting: false
         - murano-tempest-api-xena:
             voting: false
-        - murano-tempest-api-wallaby:
-            voting: false
         - murano-tempest-cfapi
 
 - job:
@@ -34,9 +32,3 @@
     parent: murano-tempest-api
     nodeset: openstack-single-node-focal
     override-checkout: stable/xena
-
-- job:
-    name: murano-tempest-api-wallaby
-    parent: murano-tempest-api
-    nodeset: openstack-single-node-focal
-    override-checkout: stable/wallaby