commit bbd2018ee19eff5594ae3986bf56fbcd0044699d changed the output format of `docker service ps`. this patch updates the reference docs to match the updated output format. Signed-off-by: Sebastiaan van Stijn <github@gone.nl> Upstream-commit: 5902fa33840507706e6e9b189fec0adeb20affa5 Component: engine