mono parameter to the Audio feature is missing

[ernestum]

According to the docs, there is a "mono" parameter to the Audio feature, which turns any stereo into mono. In practice the signal is not touched and the mono parameter, even though documented, does not exist.

https://github.com/huggingface/datasets/blob/41c05299348a499807432ab476e1cdc4143c8772/src/datasets/features/audio.py#L52C1-L54C22

[CloseChoice]

Hey, we removed the misleading passage in the docstring and enabled support for num_channels as torchcodec does

[ernestum]

thanks!