enable CommonMark as the default (EE version)
Update markdown.md
to correspond with changes for CommonMark MR in the CE repository.
Related to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19331
Update markdown.md
to correspond with changes for CommonMark MR in the CE repository.
Related to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19331