minor #34723 [FrameworkBundle] Use UserInterface to @return in getUser method (Arman-Hosseini)

This PR was squashed before being merged into the 3.4 branch.

Discussion
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[FrameworkBundle] Use UserInterface to @return in getUser method

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| License       | MIT
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Commits
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9f1ebd7fb9 [FrameworkBundle] Use UserInterface to @return in getUser method

Author: nicolas-grekas

Controller/ControllerTrait.php

@@ -26,6 +26,7 @@
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 use Symfony\Component\Security\Core\Exception\AccessDeniedException;
+use Symfony\Component\Security\Core\User\UserInterface;
 use Symfony\Component\Security\Csrf\CsrfToken;
 
 /**
@@ -431,7 +432,7 @@ protected function getDoctrine()
     /**
      * Get a user from the Security Token Storage.
      *
-     * @return object|null
+     * @return UserInterface|object|null
      *
      * @throws \LogicException If SecurityBundle is not available
      *