Updated DATASETS.md (semantic annotations in habitat-lab)

[rpartsey]

Motivation and Context

I'm not sure if loading semantic annotations in habitat-lab should be part of habitat-sim README.md, but if so, then it has to be updated to Hydra style.

Types of changes

• [x ] Docs change / refactoring / dependency upgrade

[aclegg3]

@rpartsey

not sure if loading semantic annotations in habitat-lab should be part of habitat-sim README.md

I agree we should think about how much cross-talk we have b/t lab and sim documentation. If users need to be told how to use datasets in Habitat-lab, maybe it makes more sense to have another DATASETS.md on that side instead of trying to cram it in here.