Bump symfony/http-kernel from 5.1.3 to 5.1.5 in /api

Bumps [symfony/http-kernel](https://github.com/symfony/http-kernel) from 5.1.3 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](https://github.com/symfony/http-kernel/compare/v5.1.3...v5.1.5

)

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