minor #1544 FormTrait: Fixed unused imports (chihiro-adachi)

This PR was merged into the 2.2.x-dev branch.

Discussion
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FormTrait: Fixed unused imports

Commits
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b51414f8 Fix unused components

src/Silex/Application/FormTrait.php

@@ -11,10 +11,9 @@
 
 namespace Silex\Application;
 
-use Symfony\Component\Form;
 use Symfony\Component\Form\Extension\Core\Type\FormType;
 use Symfony\Component\Form\FormBuilder;
-use Symfony\Component\OptionsResolver\OptionsResolver\FormTypeInterface;
+use Symfony\Component\Form\FormTypeInterface;
 
 /**
  * Form trait.