update mb limit

app.py

@@ -82,7 +82,7 @@ async def on_chat_start():
         files = await cl.AskFileMessage(
             content="Please upload a Text file or a PDF to begin!",
             accept=["text/plain", "application/pdf"],
-            max_size_mb=2,
+            max_size_mb=12,
             timeout=180,
         ).send()