Remove redundant local path information in audio/image datasets
Remove the redundant path information in the audio/image dataset as discussed in https://github.com/huggingface/datasets/pull/3430#issuecomment-994734828

TODOs:
* [ ] merge https://github.com/huggingface/datasets/pull/3430
* [ ] merge https://github.com/huggingface/datasets/pull/3364
* [ ] re-generate the info files of the updated audio datasets

cc:  @patrickvonplaten @anton-l @nateraw (I expect this to break the audio/vision examples in Transformers; after this change you'll be able to access underlying paths as follows `dset = dset.cast_column("audio", Audio(..., decode=False)); path = dset[0]["audio"]`)

Cool, I'm in favor of this PR. Our official examples in speech already make use of `"audio"` so no need to change anything there. It would be great if we could prominently feature how one can get the audio path without decoding in the docs. @patrickvonplaten Yes, I agree.

cc @stevhliu we should add an example where decoding is disabled (to read paths) to  [this section](https://github.com/huggingface/datasets/blob/master/docs/source/audio_process.rst#audio-datasets) in the docs and remove the mentions of `path`/`file` (if we merge this PR). Thanks @mariosasko. Are you planning to finish this before we remove the dataset scripts from GitHub? 