[Profiler] Fix data collector getCasters() call

Author: ogizanagi

Extension/DataCollector/FormDataCollector.php

@@ -16,7 +16,6 @@
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\DataCollector\DataCollector;
-use Symfony\Component\HttpKernel\DataCollector\Util\ValueExporter;
 use Symfony\Component\Validator\ConstraintViolationInterface;
 use Symfony\Component\VarDumper\Caster\Caster;
 use Symfony\Component\VarDumper\Caster\ClassStub;
@@ -68,11 +67,6 @@ class FormDataCollector extends DataCollector implements FormDataCollectorInterf
      */
     private $formsByView;
 
-    /**
-     * @var ValueExporter
-     */
-    private $valueExporter;
-
     private $hasVarDumper;
 
     public function __construct(FormDataExtractorInterface $dataExtractor)