Resolve #3490037 "Min drupal 10.3"

Closes #3490037

src/Form/AdminUninstallForm.php

 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\private_message\Form;
 
 use Drupal\Core\Form\ConfirmFormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Drupal\Core\Url;
 use Drupal\private_message\Service\PrivateMessageUninstallerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -20,7 +23,7 @@ class AdminUninstallForm extends ConfirmFormBase {
   /**
    * {@inheritdoc}
    */
-  public static function create(ContainerInterface $container) {
+  public static function create(ContainerInterface $container): self {
     return new static(
       $container->get('private_message.uninstaller')
     );
@@ -29,35 +32,35 @@ class AdminUninstallForm extends ConfirmFormBase {
   /**
    * {@inheritdoc}
    */
-  public function getFormId() {
+  public function getFormId(): string {
     return 'private_message_admin_uninstall_form';
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getQuestion() {
+  public function getQuestion(): TranslatableMarkup {
     return $this->t('Are you sure you want to delete all private message content from the system?');
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getCancelUrl() {
+  public function getCancelUrl(): Url {
     return Url::fromRoute('private_message.admin_config.uninstall');
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getDescription() {
+  public function getDescription(): TranslatableMarkup|string {
     return $this->t('Clicking the button below will delete all private message content from the system, allowing the module to be uninstalled.') . '<br><strong>' . $this->t('THIS ACTION CANNOT BE REVERSED') . '</strong>';
   }
 
   /**
    * {@inheritdoc}
    */
-  public function submitForm(array &$form, FormStateInterface $form_state) {
+  public function submitForm(array &$form, FormStateInterface $form_state): void {
     $this->privateMessageUninstaller->initiateBatch();
 
     $this->messenger()