Display recommendation message as warning, not status.

Closes #3258613

src/Form/BackupMigrateAdvancedBackupForm.php

@@ -5,6 +5,7 @@ namespace Drupal\backup_migrate\Form;
 use Drupal\backup_migrate\Drupal\Config\DrupalConfigHelper;
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Messenger\MessengerInterface;
 
 /**
  * Provides a form for performing a 1-click site backup.
@@ -24,7 +25,7 @@ class BackupMigrateAdvancedBackupForm extends FormBase {
   public function buildForm(array $form, FormStateInterface $form_state) {
     // Leave a message about the Entire Site backup.
     // @see https://www.drupal.org/project/backup_migrate/issues/3151290
-    $this->messenger()->addMessage($this->t('It is recommended to not use the "Entire site" backup as it has a tendency of failing on anything but the tiniest of sites. Hopefully this will be fixed in a future release.'));
+    $this->messenger()->addMessage($this->t('It is recommended to not use the "Entire site" backup as it has a tendency of failing on anything but the tiniest of sites. Hopefully this will be fixed in a future release.'), MessengerInterface::TYPE_WARNING);
 
     $form = [];