7 files declare their use of UserStorageInterface in Zircon Profile 8

CommentNameConstraintValidator.php in core/modules/comment/src/Plugin/Validation/Constraint/CommentNameConstraintValidator.php

Contains \Drupal\comment\Plugin\Validation\Constraint\CommentNameConstraintValidator.

ProtectedUserFieldConstraintValidator.php in core/modules/user/src/Plugin/Validation/Constraint/ProtectedUserFieldConstraintValidator.php

Contains \Drupal\user\Plugin\Validation\Constraint\ProtectedUserFieldConstraintValidator.

SiteConfigureForm.php in core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php

Contains \Drupal\Core\Installer\Form\SiteConfigureForm.

UserController.php in core/modules/user/src/Controller/UserController.php

Contains \Drupal\user\Controller\UserController.

UserLoginForm.php in core/modules/user/src/Form/UserLoginForm.php

Contains \Drupal\user\Form\UserLoginForm.

UserMultipleCancelConfirm.php in core/modules/user/src/Form/UserMultipleCancelConfirm.php

Contains \Drupal\user\Form\UserMultipleCancelConfirm.

UserPasswordForm.php in core/modules/user/src/Form/UserPasswordForm.php

Contains \Drupal\user\Form\UserPasswordForm.