add 'Advanced settings' to strings to be translated

searx/templates/oscar/advanced.html

     <input type="checkbox" id="check-advanced">
     <label for="check-advanced">
         <span class="glyphicon glyphicon-cog"></span>
-        Advanced settings
+        {{ _('Advanced settings') }}
     </label>
     <div id="advanced-search-container">
         {% include 'oscar/categories.html' %}