fix: keyError: 'model' in server, when using browser extension

[gchust]

In latest version, brower extension is not working anymore.
Here is the server side errors:

Traceback (most recent call last):
  File "/home/gchust/miniconda3/envs/whisperlive/lib/python3.11/site-packages/websockets/sync/server.py", line 499, in conn_handler
    handler(connection)
  File "/mnt/c/work/WhisperLive/whisper_live/server.py", line 168, in recv_audio
    model=options["model"],
          ~~~~~~~^^^^^^^^^
KeyError: 'model'

This is the payload send from the web browser extension

{'uid': '620a44b8-38d3-4967-8f36-df7272aa8eb4', 'multilingual': False, 'language': 'zh', 'task': 'transcribe', 'model_size': 'small'}

Looks like server expecting model from client.

After the fix, I am able to use the extension now:

[makaveli10]

Thanks for putting this together.