Bump symfony/http-kernel from 6.0.4 to 6.0.20 in /tests/Application

Bumps [symfony/http-kernel](https://github.com/symfony/http-kernel) from 6.0.4 to 6.0.20.
- [Release notes](https://github.com/symfony/http-kernel/releases)
- [Changelog](https://github.com/symfony/http-kernel/blob/7.2/CHANGELOG.md)
- [Commits](symfony/http-kernel@v6.0.4...v6.0.20)

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

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