S2S context summarization: Upgrade websockets.connect() call to v15

[gabor-openai]

Summary

In Websockets V15.0.1, the extra_headers parameter is replaced by the additional_headers parameter. Upgrade guide:
https://websockets.readthedocs.io/en/stable/howto/upgrade.html#arguments-of-connect

Motivation

The current implementation throws the following error:

Cell In[12], line 20, in realtime_session(model, voice, enable_playback)
     17 url = f"wss://api.openai.com/v1/realtime?model={model}"
     18 headers = {"Authorization": f"Bearer {openai.api_key}"}
---> 20 async with websockets.connect(url, extra_headers=headers, max_size=1 << 24) as ws:

TypeError: BaseEventLoop.create_connection() got an unexpected keyword argument 'extra_headers'