[Form] Fixed default value of 'validation_groups' option, removed duplicate definition

src/Symfony/Component/Form/Type/FieldType.php

@@ -103,7 +103,7 @@ class FieldType extends AbstractType
             'max_length' => null,
             'property_path' => null,
             'by_reference' => true,
-            'validation_groups' => true,
+            'validation_groups' => null,
             'error_bubbling' => false,
             'error_mapping' => array(),
         );

src/Symfony/Component/Form/Type/FormType.php

@@ -61,7 +61,6 @@ class FormType extends AbstractType
             'csrf_field_name' => '_token',
             'csrf_provider' => null,
             'csrf_page_id' => get_class($this),
-            'validation_groups' => null,
             'virtual' => false,
             // Errors in forms bubble by default, so that form errors will
             // end up as global errors in the root form