Two methods for disabling autosave is not working

I’m trying to turn off autosave but it’s still doing it. In wp-config.php I have:

define( 'WP_POST_REVISIONS', 3 );
define('AUTOSAVE_INTERVAL', 86400);

and in functions.php I have:

add_action( 'admin_init', 'disable_autosave' );
function disable_autosave() {
    wp_deregister_script( 'autosave' );
}

What am I missing?