docs: cli.md; document docker version output

Commit 3cec63d56f9de6332aa3f33502695283d4feb054 changed the output of
docker version. Updating docs accordingly.

Docker-DCO-1.1-Signed-off-by: Jonathan McCrohan <jmccrohan@gmail.com> (github: jmccrohan)
Merge pull request #5920 from jmccrohan/master

docs: cli.md; document docker version output