Fix: vtex discount coming negative

[bruno-monteiro1]

This PR addresses the issue of discount values coming as a negative number, while some parts of the code expect them to be positive.

One of the side effects of this issue is the wrong display of the total value in Minicart and the abscence of the discounts component inside it.

[guitavano]

I think it impacts de events triggereds, for example at "add_to_cart", google does not expect negative "discount".
https://developers.google.com/analytics/devguides/collection/ga4/reference/events?sjid=14806687593381695830-SA&hl=pt-br&client_type=gtag#add_to_cart

can you check? and maybe fix?

[bruno-monteiro1]

I found 6 instances of sendEvent usage.

The ones where the discount parameter is calculated by this code are already fixed because they end up receiving the converted value of this PR.

The others use the itemToAnalyticsItem of the useCart hook, which already returns the correct value for the discount because it subtracts the sellingPrice from the listPrice of the object, always ending up in a positive value.