Revert "Update billing.md"

src/handbook/operations/billing.md

@@ -25,7 +25,7 @@ and charge customers based on their payment method filed with Stripe.
 
 For annual subscriptions, which could also be self-managed, invoices are created
 in Stripe. These invoices are created manually *after* the customer has agreed
-on the [quote](//handbook/customer/sales/engagements/#generating-a-quote) and
+on the [quote](/handbook/customer/sales/engagements#generating-a-quote-and-order-form) and
 [terms](/handbook/customer/sales/legal/#subscription-agreement).
 
 ### Creating an invoice