erp5_core: get_fields_in_group already exclude disabled field

https://lab.nexedi.com/nexedi/erp5/blob/bb7d107124e96a6176f56226d3093d8845c3949d/product/Formulator/Form.py#L228

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Base_getListbox.py

@@ -46,6 +46,5 @@ if listbox:
 for group in ('bottom', 'center', 'left', 'right'):
   for field in form.get_fields_in_group(group):
     if (isListBox(field) and
-        not field.get_value('hidden') and
-        field.get_value('enabled')):
+        not field.get_value('hidden')):
       return field