Merge pull request #164 from arduino/dependabot/pip/black-21.9b0

Bump black from 21.8b0 to 21.9b0

Author: per1234

poetry.lock

@@ -13,7 +13,7 @@ python = "^3.9"
 [tool.poetry.dev-dependencies]
 yamllint = "^v1.26.3"
 codespell = "^2.1.0"
-black = "^21.8b0"
+black = "^21.9b0"
 flake8 = "^3.9.2"
 pep8-naming = "^0.12.1"
 pytest = "^6.2.5"