fix toc for security baseline

Author: asudbring

articles/virtual-network/toc.yml

@@ -84,6 +84,8 @@
       href: tutorial-create-route-table.md
 - name: Security
   items:
+    - name: Secure Virtual Network
+      href: secure-virtual-network.md
     - name: Azure Kubernetes network policies
       href: kubernetes-network-policies.md
     - name: Azure Policy Regulatory Compliance controls