Comment out broken link to Tor FAQ

The FAQ used to have a comparison of I2P and Tor (still visible at
http://web.archive.org/web/20100414000107/http://wiki.noreply.org/noreply/TheOnionRouter/TorFAQ#ComparisonI2P)
but it doesn't look like it's been migrated over when Tor moved to Trac and their own domain.