First of all, you should never edit a core file. Instead of editing \components\com_content\views\featured\tmpl\default_item.php
, you should make a copy of the file and place it here - /templates/YOUR TEMPLATE/html/com_content/featured/default_item.php
.
This will prevent Joomla from overwriting any changes when there is an update/upgrade. This is probably also why you are not seeing the change on your site. There is very likely a template override for \components\com_content\views\featured\tmpl\default_item.php
already in your template folder. If there is, Joomla will use that file instead of the core file you are editing. Make your changes in your template override and it should work.