minor #18456 [Form] Remove unnecessary option assignment (sergeyfedotov)

This PR was merged into the 2.3 branch.

Discussion
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[Form] Remove unnecessary option assignment

| Q             | A
| ------------- | ---
| Branch?       | 2.3
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Option assignment is not required because the prototype inherits this option from the parent form via standard inheritance mechanism.

Related pull requests: #16959, #18317

Commits
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da8a197 Remove unnecessary option assignment

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

@@ -28,7 +28,6 @@ public function buildForm(FormBuilderInterface $builder, array $options)
     {
         if ($options['allow_add'] && $options['prototype']) {
             $prototype = $builder->create($options['prototype_name'], $options['type'], array_replace(array(
-                'required' => $options['required'],
                 'label' => $options['prototype_name'].'label__',
             ), $options['options']));
             $builder->setAttribute('prototype', $prototype->getForm());