minor #39994 [FrameworkBundle] add missing use statement (xabbuh)

This PR was merged into the 5.1 branch.

Discussion
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[FrameworkBundle] add missing use statement

| Q             | A
| ------------- | ---
| Branch?       | 5.1
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Commits
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cfab105930 add missing use statement

src/Symfony/Bundle/FrameworkBundle/Tests/Controller/AbstractControllerTest.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Bundle\FrameworkBundle\Tests\Controller;
 
+use Doctrine\Persistence\ManagerRegistry;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 use Symfony\Bundle\FrameworkBundle\Tests\TestCase;
 use Symfony\Component\DependencyInjection\Container;