factorio: fix updateScript definition

The update script does not take `username` and `token` parameters anymore,
since 44754ac (thanks Luke!)

As a side-effect, R. RyanTM should now keep `factorio` up-to-date
like the good bot it is.  <3

(cherry picked from commit afa66f4)

pkgs/by-name/fa/factorio/package.nix

@@ -201,15 +201,7 @@ let
         $out/bin/factorio
     '';
 
-    passthru.updateScript =
-      if (username != "" && token != "") then
-        [
-          ./update.py
-          "--username=${username}"
-          "--token=${token}"
-        ]
-      else
-        null;
+    passthru.updateScript = ./update.py;
 
     meta = {
       description = "Game in which you build and maintain factories";