docs: highlight fixes (#8094)

www/apps/book/app/basics/modules-and-services/page.mdx

@@ -48,7 +48,7 @@ A module must have an `index.ts` file in its root directory that exports its def
 
 For example, create the file `src/modules/hello/index.ts` with the following content:
 
-```ts title="src/modules/hello/index.ts" highlights={[["5", "", "The main service of the module."]]}
+```ts title="src/modules/hello/index.ts" highlights={[["7", "", "The main service of the module."]]}
 import HelloModuleService from "./service"
 import { Module } from "@medusajs/utils"