Fix intro text for SDK v4 (#508)

As far as I know, the v4 of the C# and NodeJS SDK-s are not in preview anymore.

Author: peterbozso

articles/bot-service-quickstart.md

@@ -78,7 +78,7 @@ In this topic, you learned how to create a **Basic** Web App Bot/Functions Bot b
 # Create a bot with Azure Bot Service
 [!INCLUDE [pre-release-label](includes/pre-release-label.md)]
 
-Azure Bot Service provides the core components for creating bots, including the Bot Builder SDK for developing bots and the bot service for connecting bots to channels. In the topic, you'll be able to choose either .NET or Node.js template to create a bot using the preview version of the Bot Builder SDK v4.
+Azure Bot Service provides the core components for creating bots, including the Bot Builder SDK for developing bots and the bot service for connecting bots to channels. In the topic, you'll be able to choose either .NET or Node.js template to create a bot using the Bot Builder SDK v4.
 
 ## Log in to Azure
 Log in to the [Azure portal](http://portal.azure.com).