add_filter( 'woocommerce_cart_item_quantity', 'wc_cart_item_quantity', 10, 3 );
function wc_cart_item_quantity( $product_quantity, $cart_item_key, $cart_item ){
    if( is_cart() ){
        $product_quantity = sprintf( '%2$s <input type="hidden" name="cart[%1$s][qty]" value="%2$s" />', $cart_item_key, $cart_item['quantity'] );
    }
    return $product_quantity;
}
