change MONUMENT_API to new URL to avoid redirect garbling URL parameter

`MONUMENT_API` is set to `http://wlm.wikimedia.org/api/api.php`, which redirects to `http://toolserver.org/~erfgoed/api/api.php` now. Unfortunately the redirect reescapes the URL parameters, so the commas are changed from `%2C` to `%252C` and then don't get unescaped properly, so the search returns an error in JSON instead of results.

This patch changes the URL to avoid the redirect.