Markdown links don't work well in include files, so use a plain "HTML" link
instead.
Also removing the mention of Docker 18.09. Docker 18.09 has been released
3 years ago, so users not yet on that release (or up) did not update their
docker install for 3 years, which should be "rare" (hopefully)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>