Update welcome message for A/B Testing RAG app

app.py

@@ -235,7 +235,7 @@ The application requires preprocessing of PDF documents to build a knowledge bas
         )
         
         # Let the user know that the system is ready
-        msg.content = "Knowledge base loaded! You can now ask questions about AB Testing. We'll use material written by Ronny Kohavi to answer your questions!"
+        msg.content = "Please ask questions about A/B Testing. We'll use material written by Ronny Kohavi to answer your questions!"
         await msg.update()
         
         cl.user_session.set("chain", retrieval_augmented_qa_pipeline)