Bump flexi_logger from 0.28.0 to 0.28.1 (#559)

Bumps [flexi_logger](https://github.com/emabee/flexi_logger) from 0.28.0 to 0.28.1.
- [Changelog](https://github.com/emabee/flexi_logger/blob/master/CHANGELOG.md)
- [Commits](https://github.com/emabee/flexi_logger/commits)

---
updated-dependencies:
- dependency-name: flexi_logger
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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