Fix auth example imports in Gettings Started guide
Fix auth example imports in Gettings Started guide

Removed unused `transfer_user` import and added missing `channel_session_user_from_http` as import.
raiderrobert/channels,andrewgodwin/django-channels,django/channels,andrewgodwin/channels,Krukov/channels,linuxlewis/channels,Coread/channels,Krukov/channels,raphael-boucher/channels,Coread/channels