Deprecation: ConstraintValidatorInterface::validate()" might add "void"

Problem/Motivation

Method "Symfony\Component\Validator\ConstraintValidatorInterface::validate()" might add "void" as a native return type declaration in the future. Do the same in implementation "Drupal\genpass\Plugin\Validation\Constraint\GenpassModeConstraintValidator" now to avoid errors or add an explicit @return annotation to suppress this message.

The work in the constraint is done in 2 private functions. The interface defined method is missing the void.

In Drupal 12:

------ -----------------------------------------------------------------------
Line src/Plugin/Validation/Constraint/GenpassModeConstraintValidator.php
------ -----------------------------------------------------------------------
35 Return type mixed of method
Drupal\genpass\Plugin\Validation\Constraint\GenpassModeConstraintVali
dator::validate() is not covariant with return type void of method
Symfony\Component\Validator\ConstraintValidatorInterface::validate().
🪪 method.childReturnType (non-ignorable)
------ -----------------------------------------------------------------------

Steps to reproduce

Run phpunit tests with D11.3 core.

Proposed resolution

Add void return type to the parent method.

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