Bump black from 21.5b0 to 21.5b1 (#60)

Bumps [black](https://github.com/psf/black) from 21.5b0 to 21.5b1.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Samuel Letellier-Duchesne <samueld@mit.edu>

requirements-dev.txt

@@ -1,5 +1,5 @@
 isort==5.8.0
-black==21.5b0
+black==21.5b1
 sphinx==4.0.1
 pytest==6.2.4
 pytest-cov==2.11.1