remove redundant code in util.js

Somehow one of the commits snuck in this [redundant line](https://github.com/CodeforAustralia/school-finder/blob/master/js/util.js#L10):

```
  Handlebars.registerHelper('search_radius', function () {
    return app.config.searchRadius / 1000 + ' km';
  });
```

That can be removed. (Thanks South Australia for catching that!)