Issue #3500671 by mably: "Purge users now” button misaligned

Closes #3500671

src/Form/SettingsForm.php

@@ -356,7 +356,7 @@ class SettingsForm extends ConfigFormBase {
       '#default_value' => $config->get('send_email_user_before_notification'),
     ];
 
-    $form['purge_users_now'] = [
+    $form['actions']['purge_users_now'] = [
       '#type' => 'submit',
       '#value' => $this->t('Purge users now'),
       '#attributes' => [