All of it can be found in the manual, which defines what the
code must do, and is always up to date unlike the code comments.

We just don't need this process anymore. Less, simpler code!

API changes:

 *  Protocols start_link first argument is now Ref instead of ListenerPid
 *  ranch:accept_ack/1 argument is now Ref instead of ListenerPid
 *  ranch_listener:remove_connection/1 becomes ranch:remove_connection/1
    and its argument is now Ref instead of ListenerPid

Ref is the name of the listener given as first argument to start_listener/6.