Update webdataset call to support v0.1.48
@ericharper Can you pull this branch and verify NMT models have no issue running their WebDataset training on some toy / small dataset?

@fayejf Same for ASR Classification models

I've verified that ASR CTC/RNNT work 1:1 as before.
# Changelog
- Update API for webdataset calls
- Add lower bound for webdataset requirements (may want to pin it for release, @okuchaiev)