modules.optional.conf: example set::antirandom block: Use CIDR

instead of standard wildcard.
In this case, since it's antirandom, it is not really important
as someone is not going to add DNS records specially to avoid
triggering antirandom. That makes no sense since it is much
easier to avoid using a random looking name.
Main reason of changing it here is to set a good example.

doc/conf/modules.optional.conf

@@ -125,8 +125,8 @@ set {
 		 * NOTE: Use the REAL host or IP here, not any cloaked hosts!
 		 */
 		except-hosts {
-			mask 192.168.*;
-			mask 127.*;
+			mask 192.168.0.0/16;
+			mask 127.0.0.0/8;
 		}
 
 		/* EXCEPT-WEBIRC: