INTERNAL: update App Builder documentation links

Author: kuflower

src/pages/starter-kit/checkout/index.md

@@ -17,7 +17,6 @@ Refer to the [Getting Started](./getting-started.md) page to learn how to set up
 For more information on other technologies relevant to this project, see the following resources:
 
 - Adobe Developer Console [documentation](https://developer.adobe.com/developer-console/docs/guides/)
-- App Builder [documentation](https://developer.adobe.com/app-builder/docs/overview)
-- Adobe I/O Runtime [documentation](https://developer.adobe.com/runtime)
+- App Builder [documentation](https://developer.adobe.com/app-builder/docs/intro_and_overview/)
 - Adobe I/O Events [documentation](https://developer.adobe.com/events/docs)
 - Adobe Commerce extensibility [documentation](https://developer.adobe.com/commerce/extensibility)