Enhance `_wp_after_delete_font_family()` performance using the `fields` argument in `get_children()`.

[dilipbheda]

The _wp_after_delete_font_family() function can be optimized by leveraging the fields argument in the get_children() function. Currently, the function retrieves unnecessary data, which affects performance.

Since we use only the ID field in the wp_delete_post() function from the get_children() object, adding the fields argument will limit the query to fetch only the required IDs, improving both performance and efficiency.