We shouldn't use the git@ prefix for the private repos we hard-code.

Apparently, phabricator stores urls internally without the username.
So it has:
   https://github.com/Khan/youtube-tools
   ssh://khanacademy.kilnhg.com/Mobile-Apps/Group/android
but
   github.com:Khan/iPad

We have to change our hard-coded repo name to match.

Auditors: alpert

Test Plan:
Ran
   ./update_phabricator_repositories.py -n /tmp
and saw it say:
   Adding 0 new repositories to phabricator
   Removing 0 deleted repositories from phabricator

Without this fix, it always wanted to add and delete the ipad repo.