Rename "loaded {} batches" to "loaded {} blocks" (#1279)
Rename "loaded {} batches" to "loaded {} blocks" (#1279)

Summary:
Very small change.
The previous message was misleading, the length of TokenBlocksDataset is a number of "blocks" or "streams" but not the number of batches strictly speaking if I am not mistaken. I use the notion of batch from roberta https://github.com/pytorch/fairseq/blob/master/examples/roberta/README.pretraining.md.
It took me some time to understand what was going on, I hope it saves some time for others.
Pull Request resolved: https://github.com/pytorch/fairseq/pull/1279

Differential Revision: D18051476

fbshipit-source-id: 71fa35f21b9dbc8d6bde28cd3a487723690aadee

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq