minor #29150 Remove unused dependency in FrameworkExtensionTest (gonzalovilaseca)

This PR was submitted for the master branch but it was merged into the 4.1 branch instead (closes #29150).

Discussion
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Remove unused dependency in FrameworkExtensionTest

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? |no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

`Validation` is not used anywhere in the file, I can only see `new \ReflectionClass('Symfony\Component\Validator\Validation');`, maybe it's better to leave the `use` and replace with `new \ReflectionClass(Validation::class);`?

Commits
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aea5ca2788 Remove unused dependency

src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php

@@ -48,7 +48,6 @@ use Symfony\Component\Serializer\Normalizer\JsonSerializableNormalizer;
 use Symfony\Component\Serializer\Serializer;
 use Symfony\Component\Translation\DependencyInjection\TranslatorPass;
 use Symfony\Component\Validator\DependencyInjection\AddConstraintValidatorsPass;
-use Symfony\Component\Validator\Validation;
 use Symfony\Component\Workflow;
 
 abstract class FrameworkExtensionTest extends TestCase