Bump flake8 from 3.7.8 to 4.0.1

Bumps [flake8](https://github.com/pycqa/flake8) from 3.7.8 to 4.0.1.
- [Release notes](https://github.com/pycqa/flake8/releases)
- [Commits](PyCQA/flake8@3.7.8...4.0.1)

---
updated-dependencies:
- dependency-name: flake8
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

requirements.txt

@@ -1,7 +1,7 @@
 # Requirements for browser-calls-django
 
 # Linter
-flake8==3.7.8
+flake8==4.0.1
 
 # Django Framework
 Django==3.2.0