[FIX] website_sale_product_configurator : show correct available qty in product page

When you add items in the cart it always show the number of available left in stock of the previous state for example :
1- cart is empty it shows 20 items
2- add one into cart - it shows 20 items left in stock (should be 19)
3- add another one into cart - it show 19 items left in stock (should be 18)

Steps to reproduce the error :
1 - Go to one of the product and make sure that it has some available quantity
2 - Go to sale configuration on the product and remove "out-of-stock : continue selling" and add show available qty only if below 5000 for example
3 - Go the web page of the product and try to add some items into the cart you will see that the stock message is wrong

The origin of the problem is that when we have optional products activated , it will launch a product configurator modal. After posting the update in the database there is no call to the function that updates the stock message.

opw-3341377

closes odoo/odoo#124164

Signed-off-by: Mahdi Cheikh Rouhou (macr) <macr@odoo.com>