Update .gitreview for unmaintained/2024.1

Change-Id: I5cb26d98982b5451ce1265e0faebf48ced41b828
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

@@ -2,4 +2,4 @@
 host=review.opendev.org
 port=29418
 project=openstack/requirements.git
-defaultbranch=stable/2024.1
+defaultbranch=unmaintained/2024.1