Replace deprecated Symfony\Component\HttpKernel\DependencyInjection\Extension

[mickverm]

I noticed the following deprecation warning in our project:

User Deprecated: 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 "Doctrine\Bundle\MongoDBBundle\DependencyInjection\DoctrineMongoDBExtension".

[GromNaN]

Good catch. Thank you!

[mickverm]

That was fast 🥳