Update example config with IPv6 note for allow lists (#742)

examples/config.yml

@@ -47,8 +47,9 @@ lighthouse:
   # allowed. You can provide CIDRs here with `true` to allow and `false` to
   # deny. The most specific CIDR rule applies to each remote. If all rules are
   # "allow", the default will be "deny", and vice-versa. If both "allow" and
-  # "deny" rules are present, then you MUST set a rule for "0.0.0.0/0" as the
-  # default.
+  # "deny" IPv4 rules are present, then you MUST set a rule for "0.0.0.0/0" as
+  # the default. Similarly if both "allow" and "deny" IPv6 rules are present,
+  # then you MUST set a rule for "::/0" as the default.
   #remote_allow_list:
     # Example to block IPs from this subnet from being used for remote IPs.
     #"172.16.0.0/12": false