build(deps-dev): bump flake8 from 3.9.0 to 3.9.2

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.9.0 to 3.9.2.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.9.0...3.9.2)

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

Author: dependabot-preview[bot]

poetry.lock

@@ -38,7 +38,7 @@ black = "^20.8b1"
 pytest = "^6.2.3"
 coverage = "^5.5"
 mypy = "^0.812"
-flake8 = "^3.9.0"
+flake8 = "^3.9.2"
 flake8-bugbear = "^21.4.3"
 pytest-datadir = "^1.3.1"
 isort = "^5.8.0"