Update the Preview regions

Author: yuemlu

articles/storage/files/storage-files-identity-auth-active-directory-enable.md

@@ -5,7 +5,7 @@ author: roygara
 ms.service: storage
 ms.subservice: files
 ms.topic: conceptual
-ms.date: 03/24/2020
+ms.date: 04/01/2020
 ms.author: rogarana
 ---
 
@@ -60,10 +60,6 @@ Before you enable AD authentication for Azure file shares, make sure you have co
 
 Azure Files AD authentication (preview) is available in [most public regions](https://azure.microsoft.com/global-infrastructure/regions/).
 
-Azure Files AD authentication is not available in:
-- West US
-
-
 ## Workflow overview
 
 Before you enable AD Authentication over SMB for Azure file shares, we recommend that you walk through the [prerequisites](#prerequisites) and make sure you've completed all the steps. The prerequisites validate that your AD, Azure AD, and Azure Storage environments are properly configured.