Update per-user-access-pricing.md

Add clarification that Citrix/VMWare are not yet supported.

Author: cmckitterick

articles/virtual-desktop/remote-app-streaming/per-user-access-pricing.md

@@ -15,6 +15,9 @@ manager: femila
 
 Before external users can connect to your deployment, you need to enroll your subscription in per-user access pricing. Per-user access pricing entitles users outside of your organization to access apps and desktops in your subscription using identities that you provide and manage. Your enrolled subscription will be charged each month based on the number of distinct users that connect to Azure Virtual Desktop resources.
 
+> [!IMPORTANT]
+> Customers using Citrix DaaS or VMWare Horizon Cloud with Azure Virtual Desktop are not yet supported for per-user access pricing.
+
 >[!NOTE]
 >Take care not to confuse external *users* with external *identities*. Azure Virtual Desktop doesn't currently support external identities, including guest accounts or business-to-business (B2B) identities. Whether you're serving internal users or external users with Azure Virtual Desktop, you'll need to create and manage identities for those users yourself. Per-user access pricing is not a way to enable guest user accounts with Azure Virtual Desktop. For more information, see [Understanding licensing and per-user access pricing](licensing.md).