Issue #3262284: clean up package_manager_test_validation\TestSubscriber and classes that extend it

package_manager/tests/modules/package_manager_test_validation/src/EventSubscriber/TestSubscriber.php

 <?php
 
-namespace Drupal\package_manager_test_validation;
+namespace Drupal\package_manager_test_validation\EventSubscriber;
 
 use Drupal\Core\State\StateInterface;
 use Drupal\package_manager\Event\PostApplyEvent;