Update datasets.md
Update datasets.md

Summary:
Thanks for your contribution!

If you're sending a large PR (e.g., >50 lines),
please open an issue first about the feature / bug, and indicate how you want to contribute.

Before submitting a PR, please run `dev/linter.sh` to lint the code.

See https://detectron2.readthedocs.io/notes/contributing.html#pull-requests
about how we handle PRs.
Pull Request resolved: https://github.com/facebookresearch/detectron2/pull/1522

Differential Revision: D21852769

Pulled By: ppwwyyxx

fbshipit-source-id: 72da36af155096478ec8491f9cdc4898c31bb29d

facebookresearch/detectron2,facebookresearch/detectron2,facebookresearch/detectron2