minor #29398 [FrameworkBundle][Controller] Use interface from Contrac…

…ts to remove deprecation arnings (tomtomau)

This PR was merged into the 4.2 branch.

Discussion
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[FrameworkBundle][Controller] Use interface from Contracts to remove deprecation arnings

| Q             | A
| ------------- | ---
| Branch?       | 4.2?
| Bug fix?      | no
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | I don't think so     <!-- see https://symfony.com/bc -->
| Deprecations? | no - removing some :) <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | n/a   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | n/a

When we installed 4.2, we hit issues in our qa tools with [vimeo/psalm](https://github.com/vimeo/psalm) reporting that all of our controllers were implementing a deprecated interface (by extending the AbstractController).

This pr simply updates the AbstractController to use the interface provided in `symfony/contracts`

I'm not sure if there was any other reason for not including this in the 4.2 release (bc?), so apologies if I've overstepped this.

Commits
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f10227df3d [FrameworkBundle][Controller] Use interface from Contracts to remove deprecation warnings

Controller/AbstractController.php

@@ -15,7 +15,6 @@
 use Psr\Container\ContainerInterface;
 use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\DependencyInjection\ParameterBag\ContainerBagInterface;
-use Symfony\Component\DependencyInjection\ServiceSubscriberInterface;
 use Symfony\Component\Form\FormFactoryInterface;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\HttpFoundation\Session\SessionInterface;
@@ -27,6 +26,7 @@
 use Symfony\Component\Security\Csrf\CsrfTokenManagerInterface;
 use Symfony\Component\Serializer\SerializerInterface;
 use Symfony\Component\Templating\EngineInterface;
+use Symfony\Contracts\Service\ServiceSubscriberInterface;
 use Twig\Environment;
 
 /**