Raise WasmUnsupportedError for ffmpeg usage on Lite

[whitphx]

FFMpeg should be supported finally, but at this moment we set errors for easy debugging.

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Raise WasmUnsupportedError for ffmpeg usage on Lite

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[freddyaboulton]

I think the audio component uses ffmpeg under the hood in save_audio_to_cache functions. Playground link:

https://www.gradio.app/playground?demo=Hello_World&code=aW1wb3J0IGdyYWRpbyBhcyBncgoKZGVmIGdyZWV0KG5hbWUpOgogICAgcmV0dXJuIG5hbWUKCmRlbW8gPSBnci5JbnRlcmZhY2UoZm49Z3JlZXQsIGlucHV0cz0iYXVkaW8iLCBvdXRwdXRzPWdyLkF1ZGlvKGZvcm1hdD0ibXAzIikpCgppZiBfX25hbWVfXyA9PSAiX19tYWluX18iOgogICAgZGVtby5sYXVuY2goKQo=

[whitphx]

@freddyaboulton Correct! Thank you, I added it.

[freddyaboulton]

I would also raise if needs_conversion is True in preprocess. I am pretty sure that pydub is using ffmpeg under the hood in that case.

[freddyaboulton]

Thanks @whitphx !