:arrow_up: Bump pyyaml from 6.0.2 to 6.0.3 in /tools/serve_header (#4932)

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 6.0.2 to 6.0.3.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/6.0.3/CHANGES)
- [Commits](https://github.com/yaml/pyyaml/compare/6.0.2...6.0.3)

---
updated-dependencies:
- dependency-name: pyyaml
  dependency-version: 6.0.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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