pr review fixes

packages/medusa/src/subscribers/order.js

@@ -48,7 +48,7 @@ class OrderSubscriber {
 
     await Promise.all(
       order.discounts.map(async d => {
-        const usageCount = d?.usage_count || 0
+        const usageCount = d.rule?.usage_count || 0
         return this.discountService_.update(d.id, {
           rule: {
             ...d.rule,