fix(bil): add invoice status to faq (scaleway#4094)

Author: ldecarvalho-doc

faq/billing.mdx

@@ -76,6 +76,7 @@ The status of an invoice can be:
 * **Paid**: Refers to a fully paid invoice. No further action is required.
 * **Incomplete**: Refers to invoices where the user has provided incorrect billing details or payment information, or elements of this information are missing. The user must update this information as soon as possible to avoid having their account deleted.
 * **Outdated**: Refers to invoices where there has been a change in billing information, for example, a discount has been applied, or the client has amended their billing details. An updated invoice will be issued soon.
+* **Voided**: Refers to invoices with an amount of €0 before any discounts are applied. No further action is required.
 
 ## Do the prices shown on the website include EU VAT?