Add ms.custom metadata to index.yml

Added 'ms.custom' metadata for references regions.

Author: DivyaGundreddy

learn-pr/wwl-azure/explore-ai-governance-ai-ready-infrastructure/index.yml

@@ -7,6 +7,7 @@ metadata:
   author: wwlpublish
   ms.author: bradj
   ms.topic: module
+  ms.custom: references_regions
   ms.service: azure
 title: "Explore AI governance for AI ready infrastructure"
 summary: Learn how to govern AI workloads using Microsoft Foundry by enforcing policies, managing costs, ensuring compliance, and applying responsible AI guardrails through hands‑on governance scenarios and exercises.