XLA + IterableDataset support should now work on XLA master
🐛 Bug
Following pytorch/xla#2866 XLA should now support IterableDatasets (or at least not fail on trying to get the length). This means we can edit the check from #6875 to only fail with older XLA versions.
Note: the fix from pytorch/xla#2866 has not yet been released

Please reproduce using the BoringModel
This message from PL slack, currently gives an error: https://pytorch-lightning.slack.com/archives/CQXV8BRH9/p1618028942117600?thread_ts=1617801747.099100&cid=CQXV8BRH9