Bump flake8 from 3.8.2 to 3.8.3

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.8.2 to 3.8.3.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.8.2...3.8.3)

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

Author: dependabot-preview[bot]

requirements/lint.txt

@@ -1,5 +1,5 @@
 mypy==0.780; implementation_name=="cpython"
-flake8==3.8.2
+flake8==3.8.3
 flake8-pyi==20.5.0; python_version >= "3.6"
 black==19.10b0; python_version >= "3.6"
 mypy-extensions==0.4.3; implementation_name=="cpython"