Update .gitreview for stable/2026.1

Change-Id: I2bdc8cad8cf0ace090ca1439c5adaa004b90d0b1
Signed-off-by: OpenStack Release Bot <infra-root@openstack.org>
Generated-By: openstack/project-config:roles/copy-release-tools-scripts/files/release-tools/functions

Author: openstackadmin

.gitreview

@@ -2,3 +2,4 @@
 host=review.opendev.org
 port=29418
 project=openstack/kayobe-config.git
+defaultbranch=stable/2026.1