Correct references to --publish long syntax in docs

[lachlancooper]

This fixes the argument names in the long syntax for the --publish, --publish-add, and --publish-rm flags. The correct arguments are published and target, not target and port.

The issue is described in more detail at docker/docs#5370

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/moby/moby/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "master" git@github.com:lachlancooper/cli.git somewhere
$ cd somewhere
$ git commit --amend -s --no-edit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.

[codecov-io]

Codecov Report

Merging #746 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #746   +/-   ##
=======================================
  Coverage   53.45%   53.45%           
=======================================
  Files         218      218           
  Lines       14613    14613           
=======================================
  Hits         7811     7811           
  Misses       6321     6321           
  Partials      481      481

[mdlinville]

LGTM after you follow the instructions to sign the commit. Sorry, you can't just edit in the Github editor for this repo. Thanks for this!

[thaJeztah]

LGTM, thanks!