⬆️ Update black requirement from ^19.10b0 to ^20.8b1

Updates the requirements on [black](https://github.com/psf/black) to permit the latest version.
- [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)

---
updated-dependencies:
- dependency-name: black
  dependency-type: direct:development
...

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

pyproject.toml

@@ -11,7 +11,7 @@ docker = "^4.2.0"
 pytest = "^5.4.1"
 
 [tool.poetry.dev-dependencies]
-black = "^19.10b0"
+black = "^20.8b1"
 isort = "^4.3.21"
 autoflake = "^1.3.1"
 mypy = "^0.770"