minor #34555 [errorHandler] Remove old references from the old debug component (vincentmoulene)

This PR was submitted for the master branch but it was merged into the 5.0 branch instead.

Discussion
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[errorHandler] Remove old references from the old debug component

| Q             | A
| ------------- | ---
| Branch?       | 5.0
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

See some old references from the old debug component.
So proposal to remove.

#SymfonyHackday

Commits
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326df983ca [errorHandler] Remove old references from the old debug component

src/Symfony/Component/ErrorHandler/DebugClassLoader.php

@@ -399,7 +399,6 @@ class DebugClassLoader
         if (
             'Symfony\Bridge\PhpUnit\Legacy\SymfonyTestsListenerForV7' === $class
             || 'Symfony\Bridge\PhpUnit\Legacy\SymfonyTestsListenerForV6' === $class
-            || 'Test\Symfony\Component\Debug\Tests' === $refl->getNamespaceName()
         ) {
             return [];
         }

src/Symfony/Component/ErrorHandler/Tests/Exception/FlattenExceptionTest.php

@@ -12,7 +12,6 @@
 namespace Symfony\Component\ErrorHandler\Tests\Exception;
 
 use PHPUnit\Framework\TestCase;
-use Symfony\Component\Debug\Exception\FatalThrowableError;
 use Symfony\Component\ErrorHandler\Exception\FlattenException;
 use Symfony\Component\HttpFoundation\Exception\SuspiciousOperationException;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;