Add author name before their message in Chainlit team sample (#5878)

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## Why are these changes needed?

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solves. -->
This PR makes it clear which agent is speaking per message in the
Chainlit team sample. Previously, messages would be exchanged without
showing who is communicating.

## Related issue number

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Closes #5609 

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<https://microsoft.github.io/autogen/>. See
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introduced in this PR.
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Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>

python/samples/agentchat_chainlit/app_team.py

@@ -79,7 +79,7 @@ async def chat(message: cl.Message) -> None:
             # Stream the model client response to the user.
             if streaming_response is None:
                 # Start a new streaming response.
-                streaming_response = cl.Message(content="", author=msg.source)
+                streaming_response = cl.Message(content=msg.source + ": ", author=msg.source)
             await streaming_response.stream_token(msg.content)
         elif streaming_response is not None:
             # Done streaming the model client response.