Bump flake8 from 3.8.3 to 3.8.4 (#207)

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.8.3 to 3.8.4.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.8.3...3.8.4)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -18,7 +18,7 @@ wheel==0.35.1
 anyio==2.0.2
 autoflake==1.4
 black==20.8b1
-flake8==3.8.3
+flake8==3.8.4
 flake8-bugbear==20.1.4
 flake8-pie==0.6.1
 isort==5.5.4