Comment out 6668 bindings in default config

These are just used as examples, and prevent Oragono from starting
up if the host doesn't have an IPv6 stack (e.g. inside docker
containers).

See oragono/oragono-docker#5

oragono.yaml

@@ -13,9 +13,10 @@ server:
     # addresses to listen on
     listen:
         - ":6667"
-        - "127.0.0.1:6668"
-        - "[::1]:6668"
         - ":6697" # ssl port
+        # Binding on specific IPs:
+        # - "127.0.0.1:6668"
+        # - "[::1]:6668"
         # Unix domain socket for proxying:
         # - "/tmp/oragono_sock"