Bump flake8 from 5.0.3 to 5.0.4 in /glean-core/python

Bumps [flake8](https://github.com/pycqa/flake8) from 5.0.3 to 5.0.4.
- [Release notes](https://github.com/pycqa/flake8/releases)
- [Commits](https://github.com/pycqa/flake8/compare/5.0.3...5.0.4)

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

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

glean-core/python/requirements_dev.txt

@@ -1,7 +1,7 @@
 auditwheel==5.1.2
 black==22.6.0
 coverage==6.2
-flake8==5.0.3
+flake8==5.0.4
 flake8-bugbear==22.7.1
 jsonschema==3.2.0
 mypy==0.971