[tor-wiki-changes] org/teams/NetworkTeam/Sponsor4Design edited

[Tor Bug Tracker & Wiki: teor]

Explain why we choose 3 directory guards for idea 10 

([diff](https://trac.torproject.org/projects/tor/wiki/org/teams/NetworkTeam/Sponsor4Design?action=diff&version=7))

URL: https://trac.torproject.org/projects/tor/wiki/org/teams/NetworkTeam/Sponsor4Design?version=7