Bump guzzlehttp/guzzle in /examples/distributed-tracing/src

Bumps [guzzlehttp/guzzle](https://github.com/guzzle/guzzle) from 7.4.3 to 7.4.4.
- [Release notes](https://github.com/guzzle/guzzle/releases)
- [Changelog](https://github.com/guzzle/guzzle/blob/master/CHANGELOG.md)
- [Commits](guzzle/guzzle@7.4.3...7.4.4)

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

Signed-off-by: dependabot[bot] <[email protected]>