sca: remove misleading comment.

- suggestion in comment has long since been implemented

modules/sca/sca_subscribe.c

@@ -1245,7 +1245,6 @@ sca_handle_subscribe( sip_msg_t *msg, char *p1, char *p2 )
 	goto done;
     }
 
-    /* XXX this should be locked; could use a filled-in req_sub */
     if ( sca_notify_subscriber( sca, &req_sub, app_idx ) < 0 ) {
 	LM_ERR( "SCA %s SUBSCRIBE+NOTIFY for %.*s failed",
 		sca_event_name_from_type( req_sub.event ),