Merge branch 'correct-markdown-documentation' into 'master'

Correct markdown.md docs RE use in commit messages.

This is an improvement to the situation covered in issue #1582. It corrects the markdown documentation to demonstrate that GFM cannot currently be used in commit messages.

See merge request !1343

doc/markdown/markdown.md

@@ -33,7 +33,6 @@ For GitLab we developed something we call "GitLab Flavored Markdown" (GFM). It e
 
 You can use GFM in
 
-- commit messages
 - comments
 - issues
 - merge requests