Update model deployment policy name to include 'Preview'

Author: jonburchel

articles/ai-foundry/toc-files/security-governance/toc.yml

@@ -22,7 +22,7 @@ items:
     href: ../../how-to/disable-local-auth.md
 - name: Azure policies
   items:
-  - name: Manage model deployment policy
+  - name: Manage model deployment policy (Preview)
     href: ../../how-to/model-deployment-policy.md
   - name: Built-in policy definitions
     displayName: samples, policies, definitions, Azure Policy