tests: Bump DevStack to Caracal (2024.1)

Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

Author: stephenfin

tests/playbooks/roles/install-devstack/defaults/main.yaml

@@ -1,7 +1,7 @@
 ---
 user: "stack"
 workdir: "/home/{{ user }}/devstack"
-branch: "stable/2023.2"
+branch: "stable/2024.1"
 enable_services:
   - nova
   - glance