Add victoria/wallaby stable branch jobs on master gate

We have stable/victoria and stable/wallaby released so we
should add their job on master gate to keep branchless
tempest plugins compatible to those branch.

This also removes the stable/stein job as that is in EM
state now.

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

Change-Id: I315dc315049583e7f3bb4c8716f59b57a3229b52

.zuul.yaml

@@ -9,9 +9,10 @@
         - freezer-tempest-scheduler
         - freezer-tempest-agent
         - freezer-tempest-basic-sql
+        - freezer-tempest-basic-wallaby
+        - freezer-tempest-basic-victoria
         - freezer-tempest-basic-ussuri
         - freezer-tempest-basic-train
-        - freezer-tempest-basic-stein
 
     gate:
       queue: freezer
@@ -88,6 +89,16 @@
       devstack_localrc:
         FREEZER_BACKEND: 'sqlalchemy'
 
+- job:
+    name: freezer-tempest-basic-wallaby
+    parent: freezer-tempest-basic
+    override-checkout: stable/wallaby
+
+- job:
+    name: freezer-tempest-basic-victoria
+    parent: freezer-tempest-basic
+    override-checkout: stable/victoria
+
 - job:
     name: freezer-tempest-basic-ussuri
     parent: freezer-tempest-basic
@@ -102,12 +113,3 @@
     vars:
       devstack_localrc:
         USE_PYTHON3: True
-
-- job:
-    name: freezer-tempest-basic-stein
-    parent: freezer-tempest-basic
-    nodeset: openstack-single-node-bionic
-    override-checkout: stable/stein
-    vars:
-      devstack_localrc:
-        USE_PYTHON3: True