Fix broken links in billing intro

wix-billing-backend/wix-billing-backend.service.json

@@ -13,8 +13,8 @@
           "and [create and manage price quotes](https://support.wix.com/en/article/wix-price-quotes-creating-and-sending-price-quotes-to-clients).",
           "",
           " With the Wix billing APIs, you can:",
-          " - Manage [invoices](wix-billing-backend/invoices).",
-          " - Manage [price quotes](wix-billing-backend/pricequotes).",
+          " - Manage [invoices](/invoices/introduction).",
+          " - Manage [price quotes](/price-quotes/introduction).",
           " - Create custom handling in response to backend [invoice events](wix-billing-backend/events/introduction).",
           " - Create custom handling in response to backend [price quote events](wix-billing-backend/events/introduction).",
           " ",
@@ -29,7 +29,7 @@
           " It’s important to note the following points before starting to code:    ",
           "",
           " Invoices is an online payment request system and not an accounting service. ",
-          " In order to accept payments from customers in Wix Invoices, you must set up a [payment method](https://support.wix.com/en/article/setting-up-payment-methods-in-wix-invoices).",
+          " In order to accept payments from customers in Wix Invoices, you must set up a [payment method](https://support.wix.com/en/article/accepting-payments-an-overview).",
           " ",
           "## Terminology",
           "",
@@ -91,4 +91,4 @@
   "messages": [],
   "extra":
     { "scopes":
-        [ "backend" ] } }
+        [ "backend" ] } }