Disable the new user notification email for both admin and user
<?php
/*
 * Plugin Name: Easy Digital Downloads - Disable New User Notifications
 * Description: Disable the new user notification email for both admin and user
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

remove_action( 'edd_insert_user', 'edd_new_user_notification', 10, 2 );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.