fix(medusa): Correct inventory quantity calculation (#3881)

* initial fix

* add changeset

.changeset/ninety-foxes-approve.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/medusa": patch
+---
+
+Fix(medusa): inventory quantity calculations

packages/medusa/src/services/product-variant-inventory.ts

@@ -674,7 +674,7 @@ class ProductVariantInventoryService extends TransactionBaseService {
         })
 
         variant.inventory_quantity = locations.reduce(
-          (acc, next) => acc + (next.stocked_quantity || 0),
+          (acc, next) => acc + (next.stocked_quantity - next.reserved_quantity),
           0
         )