Updated PBIRS requirement as an Important item

Customers are missing the fact that PBIRS is required to have the load balancer configured for sticky sessions/affinity/persistence. Adding it as an Important item and providing some more explanation as to why it's required.

Author: JoshGer

docs/reporting-services/install-windows/configure-a-native-mode-report-server-scale-out-deployment.md

@@ -1,7 +1,7 @@
 ---
 description: "Configure a Native Mode Report Server Scale-Out Deployment"
 title: "Configure a Native Mode Report Server Scale-Out Deployment | Microsoft Docs"
-ms.date: 11/29/2018
+ms.date: 05/17/2021
 ms.prod: reporting-services
 ms.prod_service: "reporting-services-native"
 
@@ -21,7 +21,8 @@ ms.author: maggies
 
 Reporting Services native mode supports a scale-out deployment model that allows you to run multiple report server instances that share a single report server database. Scale-out deployments are used to increase scalability of report servers to handle more concurrent users and larger report execution loads. It can also be used to dedicate specific servers to process interactive or scheduled reports.
 
-For Power BI Report Server, you need to configure client affinity (sometimes called sticky sessions) on the load balancer for any scale-out environment, to ensure proper performance.  
+> [!IMPORTANT]
+> For Power BI Report Server, you need to configure client affinity (sometimes called sticky sessions or persistence) on the load balancer for any scale-out environment to ensure proper performance and consistent Power BI (PBIX) report functionality.
   
 For SQL Server 2016 Reporting Services and earlier, SharePoint mode report servers utilize the SharePoint products infrastructure for scale-out. SharePoint mode scale-out is performed by adding more SharePoint mode report servers to the SharePoint farm. For information on scale-out in SharePoint mode, see [Add an Additional Report Server to a Farm (SSRS Scale-out)](../../reporting-services/install-windows/add-an-additional-report-server-to-a-farm-ssrs-scale-out.md).