build(deps-dev): bump types-python-dateutil

Bumps [types-python-dateutil](https://github.com/python/typeshed) from 2.9.0.20240316 to 2.9.0.20240821.
- [Commits](https://github.com/python/typeshed/commits)

---
updated-dependencies:
- dependency-name: types-python-dateutil
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]