Bump black from 21.4b2 to 21.5b0 (#94)

Bumps [black](https://github.com/psf/black) from 21.4b2 to 21.5b0.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/master/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Brett Cannon <[email protected]>

Author: dependabot[bot]

dev-requirements.txt

@@ -8,7 +8,7 @@ appdirs==1.4.4
     # via black
 attrs==20.3.0
     # via pytest
-black==21.4b2
+black==21.5b0
     # via -r dev-requirements.in
 click==7.1.2
     # via black