Remove duplicated description of --mtu

commit baa70e975186bb0ee8a4b16b9374cb6e794f8975 duplicates
the description of --mtu.
This patch removes the duplicated description.

Docker-DCO-1.1-Signed-off-by: Ken ICHIKAWA <ichikawa.ken@jp.fujitsu.com> (github: ichik1)
Add missing options -t and -v to images subcommand doc

Docker-DCO-1.1-Signed-off-by: Ken ICHIKAWA <ichikawa.ken@jp.fujitsu.com> (github: ichik1)
Merge pull request #4638 from ichik1/cli-doc-minor-fix

Some minor fixes for cli docs