minor #40728 [PHPDoc] Fix some union type cases (fancyweb)

This PR was merged into the 4.4 branch.

Discussion
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[PHPDoc] Fix some union type cases

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

While working on symfony/symfony#40154, I discovered some PHPDoc issues, I'm going to comment in the review. Upper branches will need some fixes too.

Commits
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dd1481642b [PHPDoc] Fix some union type cases

Author: Nyholm

Extension/Validator/Constraints/FormValidator.php

@@ -202,7 +202,7 @@ public function validate($form, Constraint $formConstraint)
     /**
      * Returns the validation groups of the given form.
      *
-     * @return string|GroupSequence|(string|GroupSequence)[] The validation groups
+     * @return string|GroupSequence|array<string|GroupSequence> The validation groups
      */
     private function getValidationGroups(FormInterface $form)
     {
@@ -241,9 +241,9 @@ private function getValidationGroups(FormInterface $form)
     /**
      * Post-processes the validation groups option for a given form.
      *
-     * @param string|GroupSequence|(string|GroupSequence)[]|callable $groups The validation groups
+     * @param string|GroupSequence|array<string|GroupSequence>|callable $groups The validation groups
      *
-     * @return GroupSequence|(string|GroupSequence)[] The validation groups
+     * @return GroupSequence|array<string|GroupSequence> The validation groups
      */
     private static function resolveValidationGroups($groups, FormInterface $form)
     {