Update toc.yml

Adding entry for the article on Azure Policy

Author: Nagarjuna-Vipparthi

articles/load-testing/toc.yml

@@ -95,6 +95,8 @@ items:
           href: how-to-use-a-managed-identity.md
         - name: Configure customer-managed keys
           href: how-to-configure-customer-managed-keys.md
+        - name: Secure Azure Load Testing with Azure Policy
+          href: how-to-use-azure-policy.md
     - name: Manage resources
       items:
         - name: Create & manage tests (Azure portal)