Revert "Document port6 and bind6 config options."

IPv6 support is not going to use IPv6 specific options, just it will be
possible to specify all the ipv4 / ipv6 addresses of the interfaces to
bind, otherwise connections will be accepted from all the interfaces in
both IPv4 and IPv6 addresses.

This reverts commit 93570e17.

redis.conf

@@ -23,7 +23,6 @@ pidfile /var/run/redis.pid
 # Accept connections on the specified port, default is 6379.
 # If port 0 is specified Redis will not listen on a TCP socket.
 port 6379
-# port6 6379
 
 # By default Redis listens for connections from all the network interfaces
 # available on the server. It is possible to listen to just one or multiple
@@ -34,7 +33,6 @@ port 6379
 #
 # bind 192.168.1.100 10.0.0.1
 # bind 127.0.0.1
-# bind6 ::1
 
 # Specify the path for the unix socket that will be used to listen for
 # incoming connections. There is no default, so Redis will not listen