Drop special treatment of Tails vs account creation.
Drop special treatment of Tails vs account creation.

The extensions.torbirdy.emailwizard pref is enough for Tails'
purposes, so let's clean up a bit.

kartikm/torbirdy,infertux/torbirdy,u451f/torbirdy,ioerror/torbirdy,u451f/torbirdy,ioerror/torbirdy,kartikm/torbirdy,infertux/torbirdy