disable markdown in comments when referencing disabled features
fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/23548
This MR prevents the following references when tool is disabled:
- issues
- snippets
- commits - when repo is disabled
- commit range - when repo is disabled
- milestones
This MR does not prevent references to repository files, since they are just markdown links and don't leak
information.
See merge request !2011
Signed-off-by: Rémy Coutable <remy@rymai.me>
