Copy this following code and save as disable_email.php . Then place that file in "wp-content/plugins/" directory. And active from Admin Panel.

    <?php
    /*
    Plugin Name: Stop email change password
    Description: Whatever
    */
            
    if (!function_exists('wp_password_change_notification')) {
        function wp_password_change_notification($user) {
            return;
        }
    }
    ?>