add info on linux per GitHub issue

Author: mrbullwinkle

articles/azure-monitor/app/azure-web-apps.md

@@ -24,7 +24,7 @@ There are two ways to enable application monitoring for Azure App Services hoste
 
     * This approach is much more customizable, but it requires [adding a dependency on the Application Insights SDK NuGet packages](https://docs.microsoft.com/azure/azure-monitor/app/asp-net). This method, also means you have to manage the updates to the latest version of the packages yourself.
 
-    * If you need to make custom API calls to track events/dependencies not captured by default with agent-based monitoring, you would need to use this method. Check out the [API for custom events and metrics article](https://docs.microsoft.com/azure/azure-monitor/app/api-custom-events-metrics) to learn more.
+    * If you need to make custom API calls to track events/dependencies not captured by default with agent-based monitoring, you would need to use this method. Check out the [API for custom events and metrics article](https://docs.microsoft.com/azure/azure-monitor/app/api-custom-events-metrics) to learn more. This is also currently the only supported option for Linux based workloads.
 
 > [!NOTE]
 > If both agent-based monitoring and manual SDK-based instrumentation is detected, only the manual instrumentation settings will be honored. This is to prevent duplicate data from being sent. To learn more about this, check out the [troubleshooting section](https://docs.microsoft.com/azure/azure-monitor/app/azure-web-apps#troubleshooting) below.