[Form] Removed dead code in the buildForm method of DateType.php

 * With the introduction of the getAllowedOptionValues mechanics, the check
   is performed prior to the buildForm call. There is no more needs to check
   it again in DateType.

src/Symfony/Component/Form/Extension/Core/Type/DateType.php

@@ -14,7 +14,6 @@ namespace Symfony\Component\Form\Extension\Core\Type;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormInterface;
 use Symfony\Component\Form\FormBuilder;
-use Symfony\Component\Form\Exception\FormException;
 use Symfony\Component\Form\Extension\Core\ChoiceList\PaddedChoiceList;
 use Symfony\Component\Form\Extension\Core\ChoiceList\MonthChoiceList;
 use Symfony\Component\Form\FormView;
@@ -80,8 +79,6 @@ class DateType extends AbstractType
             $builder->appendNormTransformer(new ReversedTransformer(
                 new DateTimeToArrayTransformer($options['data_timezone'], $options['data_timezone'], array('year', 'month', 'day'))
             ));
-        } else if ($options['input'] !== 'datetime') {
-            throw new FormException('The "input" option must be "datetime", "string", "timestamp" or "array".');
         }
 
         $builder