⬆️ Update black requirement from ^19.10b0 to ^20.8b1 (#28)

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/master/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>

pyproject.toml

@@ -42,7 +42,7 @@ shellingham = "^1.3.2"
 
 [tool.poetry.dev-dependencies]
 pytest = "^6.0.1"
-black = {version = "^19.10b0", allow-prereleases = true}
+black = {version = "^20.8b1", allow-prereleases = true}
 pytest-cov = "^2.8.1"
 pytest-xdist = "^1.31.0"
 pytest-sugar = "^0.9.2"