Update guzzlehttp/guzzle requirement in /build/integration

Updates the requirements on [guzzlehttp/guzzle](https://github.com/guzzle/guzzle) to permit the latest version.
- [Release notes](https://github.com/guzzle/guzzle/releases)
- [Changelog](https://github.com/guzzle/guzzle/blob/6.5.5/CHANGELOG.md)
- [Commits](https://github.com/guzzle/guzzle/compare/6.5.2...6.5.5

)

---
updated-dependencies:
- dependency-name: guzzlehttp/guzzle
  dependency-type: direct:development
...

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