Bump pyproject-flake8 from 0.0.1a3 to 0.0.1a4 (#1447)

Bumps [pyproject-flake8](https://github.com/csachs/pyproject-flake8) from 0.0.1a3 to 0.0.1a4.
- [Release notes](https://github.com/csachs/pyproject-flake8/releases)
- [Commits](csachs/pyproject-flake8@v0.0.1a3...v0.0.1a4)

---
updated-dependencies:
- dependency-name: pyproject-flake8
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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