Bump symfony/http-kernel in /src/unprotected-server/hello

Bumps [symfony/http-kernel](https://github.com/symfony/http-kernel) from 6.0.6 to 6.0.20.
- [Release notes](https://github.com/symfony/http-kernel/releases)
- [Changelog](https://github.com/symfony/http-kernel/blob/7.1/CHANGELOG.md)
- [Commits](symfony/http-kernel@v6.0.6...v6.0.20)

---
updated-dependencies:
- dependency-name: symfony/http-kernel
  dependency-type: indirect
...

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Author: dependabot[bot]