Django Geoposition - customize admin widget

Question

I'm trying to remove a field from the django-geoposition admin widget. This field:

I tried going to the source site-packages/geoposition/static/geoposition/geoposition.css and adding display:none to the relevant css class:

.geoposition-search {
    display: none;
    width: 30%;
}

That didn't work. How can I customize this widget?