4.md - Update API Reference

Update the API reference to remain consistent and tell users to pick the proper API version.

Author: LaurenMalhoit

labs/coding-101-rest-basics-ga/4.md

@@ -20,7 +20,7 @@ https://{APIC-EM-Server}/api/v1
 
 ```
 
-Get the description of the ticket API call from the -- <a href="http://devnetapic.cisco.com" target="_blank">APIC-EM API Docs</a>.
+Get the description of the ticket API call from the -- <a href="https://developer.cisco.com/site/apic-em/docs/api.html?version=1.6" target="_blank">APIC-EM API Docs</a>. Choose the proper API version.
 
 `POST /api/v1/ticket`: This method creates a new user ticket