Woocommerce orders goes to COMPLETE status on their own

I added the code below in the function.php child theme to have my Woocommerce orders status directly set to COMPLETE but this code prevented another woocommerce plugin from working properly. so i removed it from the function.php file completely, however the status of new order still are set to COMPLETE and i cant understand why its still doing that, is the function.php file somehow cached? is there a way to flush the cache?

/*
 * Auto Complete all WooCommerce orders.
*/
add_action( 'woocommerce_thankyou', 'custom_woocommerce_auto_complete_order' );
function custom_woocommerce_auto_complete_order( $order_id ) { 
    if ( ! $order_id ) {
        return;
    }

    $order = wc_get_order( $order_id );
    $order->update_status( 'completed' );
}