Add ai-usage metadata and update visibility in index.yml

Updated the index.yml file to include 'ai-usage' metadata and modified the visibility of the module.

Author: staleycyn

learn-pr/wwl-azure/design-ai-workloads/index.yml

@@ -8,7 +8,7 @@ metadata:
   ms.author: cynthist
   ms.topic: module
   ms.service: azure-ai-services
-  hidden: false
+  ai-usage: ai-assisted
 title: "Design AI Workloads on Azure"
 summary: Learn to design AI workloads using SaaS, PaaS, and IaaS solutions while aligning AI strategy with business goals and applying governance best practices.
 abstract: |