Break the fork link.

[erwangranger]

I'm afraid someone will click "sync" by mistake in GH and we'll have a problem.

[guimou]

It seems to be an advanced admin task, although the is a wizard to help: https://support.github.com/contact?tags=rr-forks&subject=Detach%20Fork&flow=detach_fork
It's not a standard settings, they have to do something on GitHub side, the wizard only opens the ticket.
I'm putting this on hold at the moment, we don't want to take any risk before Summit.