docker_swarm_service: Specify choices on update_order (#52741)

* Specify choices on update_order

* Drop quoting

* Add changelog fragment

* Revert "Add changelog fragment"

This reverts commit 6a4a2b903b859a41356ff55a8937da976345755d.

lib/ansible/modules/cloud/docker/docker_swarm_service.py

@@ -464,6 +464,9 @@ options:
       - Corresponds to the C(--update-order) option of C(docker service create).
       - Requires API version >= 1.29.
     type: str
+    choices:
+        - stop-first
+        - start-first
   user:
     description:
       - Sets the username or UID used for the specified command.
@@ -1790,7 +1793,7 @@ def main():
         update_failure_action=dict(type='str', choices=['continue', 'pause']),
         update_monitor=dict(type='raw'),
         update_max_failure_ratio=dict(type='float'),
-        update_order=dict(type='str'),
+        update_order=dict(type='str', choices=['stop-first', 'start-first']),
         user=dict(type='str'),
         working_dir=dict(type='str'),
     )