fix: DI Extension deprecated since Symfony 7.1

[AirBair]

Subject

Since Symfony 7.1:

The "Symfony\Component\HttpKernel\DependencyInjection\Extension" class is considered internal since Symfony 7.1, to be deprecated in 8.1; use Symfony\Component\DependencyInjection\Extension\Extension instead. It may change without further notice. You should not use it from "Sonata\AdminBundle\DependencyInjection\SonataAdminExtension".

Related Symfony PR: https://github.com/symfony/symfony/pull/53801

I am targeting this branch, because these changes are BC.

Changelog

### Fixed
- Symfony 7.1 deprecation about `Symfony\Component\HttpKernel\DependencyInjection\Extension` usage

Other bundles like SonataBlockExtension, SonataFormExtension, etc. have the same deprecation, will take care of them if this proposed fix is ok for you.

[VincentLanglet]

Can you also bump the rector version in the composer.json ? It will fix the rector CI.

[VincentLanglet]

Thanks