add_action( 'wp_footer', 'bbloomer_cart_refresh_update_qty' );

function bbloomer_cart_refresh_update_qty() {
    if (is_cart()) {
        ?>
        <script type="text/javascript">
            jQuery('div.woocommerce').on('click', 'input.qty', function(){
                jQuery("[name='update_cart']").trigger("click");
            });
        </script>
        <?php
    }
}