docs: fix imports from dist (#9401)

www/apps/book/app/advanced-development/api-routes/validation/page.mdx

@@ -49,7 +49,7 @@ For example, create the file `src/api/middlewares.ts` with the following content
 import { defineMiddlewares } from "@medusajs/medusa"
 import { 
   validateAndTransformBody,
-} from "@medusajs/medusa/dist/api/utils/validate-body"
+} from "@medusajs/medusa/api/utils/validate-body"
 import { PostStoreCustomSchema } from "./custom/validators"
 
 export default defineMiddlewares({