Sync docker/docker refs with files mistakenly edited in docker.github.io repo

Signed-off-by: Misty Stanley-Jones <misty@docker.com>
Upstream-commit: 3b36f02c03ec050aa46f9a01cd2d6c60ffd93652
Component: engine

components/engine/docs/reference/commandline/stack_services.md

@@ -5,6 +5,15 @@ keywords: ["stack, services"]
 advisory: "experimental"
 ---
 
+<!-- This file is maintained within the docker/docker Github
+     repository at https://github.com/docker/docker/. Make all
+     pull requests against that repo. If you see this file in
+     another repository, consider it read-only there, as it will
+     periodically be overwritten by the definitive file. Pull
+     requests which include edits to this file in other repositories
+     will be rejected.
+-->
+
 # stack services (experimental)
 
 ```markdown