Add Prerequisite on physical iOS device

Author: pavelprystinka

articles/communication-services/how-tos/ui-library-sdk/includes/pip/ios.md

@@ -10,7 +10,7 @@ ms.service: azure-communication-services
 
 For more information, see the [open-source iOS UI Library](https://github.com/Azure/communication-ui-library-ios) and the [sample application code](https://github.com/Azure-Samples/communication-services-ios-quickstarts/tree/main/ui-calling).
 
-## Prerequisites
+### Prerequisites
 A physical iOS device to run the App. An iOS Simulator does not support Picture-in-picture functionality.
 
 ### Picture-in-picture setup