avoid whitespace in rendered html output

Resources/views/Pager/base_results.html.twig

@@ -24,7 +24,7 @@ file that was distributed with this source code.
     <select class="per-page small form-control" id="{{ admin.uniqid }}_per_page" style="width: auto">
         {% for per_page in admin.getperpageoptions %}
             <option {% if per_page == admin.datagrid.pager.maxperpage %}selected="selected"{% endif %} value="{{ admin.generateUrl('list', {'filter': admin.datagrid.values|merge({'_page': 1, '_per_page': per_page})}) }}">
-                {{ per_page }}
+                {{- per_page -}}
             </option>
         {% endfor %}
     </select>