minor #16159 [Form] Typo in validation_group_service_resolver.rst (askeita)

This PR was submitted for the 5.3 branch but it was merged into the 4.4 branch instead.

Discussion
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[Form] Typo in validation_group_service_resolver.rst

Corrected namespace of ValidationGroupResolver.

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Commits
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bf8fa81 Typo in validation_group_service_resolver.rst

Author: javiereguiluz

form/validation_group_service_resolver.rst

@@ -38,7 +38,7 @@ Then in your form, inject the resolver and set it as the ``validation_groups``::
     // src/Form/MyClassType.php;
     namespace App\Form;
 
-    use App\Validator\ValidationGroupResolver;
+    use App\Validation\ValidationGroupResolver;
     use Symfony\Component\Form\AbstractType;
     use Symfony\Component\OptionsResolver\OptionsResolver;