Bump flake8 from 3.9.1 to 3.9.2

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.9.1 to 3.9.2.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.9.1...3.9.2)

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

Author: dependabot-preview[bot]

requirements.txt

@@ -7,7 +7,7 @@ marshmallow>=3.0,<4.0
 pytest
 pytest-django==3.8.0
 pytest-cov==2.11.1
-flake8==3.9.1
+flake8==3.9.2
 
 # MkDocs for documentation
 mkdocs