Bump symfony/http-kernel from 5.0.8 to 5.1.5

Bumps [symfony/http-kernel](https://github.com/symfony/http-kernel) from 5.0.8 to 5.1.5.
- [Release notes](https://github.com/symfony/http-kernel/releases)
- [Changelog](https://github.com/symfony/http-kernel/blob/master/CHANGELOG.md)
- [Commits](symfony/http-kernel@v5.0.8...v5.1.5)

Signed-off-by: dependabot[bot] <support@github.com>