Update TOC.yml

Adding Preview tag

Author: saurabh0501

articles/storage/container-storage/TOC.yml

@@ -17,7 +17,7 @@
   items:
   - name: Use with Azure Disks
     href: use-container-storage-with-managed-disks.md
-  - name: Use with Azure Elastic SAN
+  - name: Use with Azure Elastic SAN (Preview)
     href: use-container-storage-with-elastic-san.md
   - name: Use with Ephemeral Disk
     items:
@@ -84,4 +84,4 @@
   items:
   - name: Pricing for Azure Container Storage
     href: https://azure.microsoft.com/pricing/details/container-storage/
-  
+