Remove deprecated `#forked_from?` check
Remove deprecated `#forked_from?` check

I forgot to clean up this bit in we switched the `forked_from_project`
relation to use fork networks in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22226

mmkassem/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq