Update advantages to GitHub

• Attach all types of files to issues
• Wip protection
• Approved (EE only)
• Remove git annex
• Maybe there are more

First we already have: https://about.gitlab.com/better-than-github/#attachments-in-issues

Status changed to closed

Fixed with ca499597

@JobV

1. Can you link to WIP docs?
2. Can you link to Approver docs?

Status changed to reopened

@sytses of course, honestly don't know why I didn't do that already: e1c6de64

Status changed to closed

@JobV Thanks!