Bump flake8 in /gtfs/gtfs_rt_producer/gtfs_rt_producer_kafka_producer (#36)

Bumps [flake8](https://github.com/pycqa/flake8) from 7.1.0 to 7.3.0.
- [Commits](PyCQA/flake8@7.1.0...7.3.0)

---
updated-dependencies:
- dependency-name: flake8
  dependency-version: 7.3.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]