Add stable/2026.2 job

The branch was created so we should start testing it.

Change-Id: Ie64518d5da659311b2b1e9665e0471bf7f1e2244
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

.zuul.yaml

@@ -37,6 +37,12 @@
       devstack_local_conf:
         post-config: {}
 
+- job:
+    name: keystone-tempest-2026-2
+    parent: keystone-tempest
+    nodeset: openstack-single-node-noble
+    override-checkout: stable/2026.2
+
 - job:
     name: keystone-tempest-2026-1
     parent: keystone-tempest
@@ -65,6 +71,7 @@
         - keystone-tempest-federation:
             voting: false
         - keystone-tempest-federation-k2k
+        - keystone-tempest-2026-2
         - keystone-tempest-2026-1
         - keystone-tempest-2025-2
         - keystone-tempest-2025-1