Issue #3046085 by kavbiswa, imalabya, joachim: Update deprecated Unicode::* to mb_*

email_registration.module

@@ -5,7 +5,6 @@
  * Allows users to register with an email address as their username.
  */
 
-use Drupal\Component\Utility\Unicode;
 use Drupal\user\UserInterface;
 use Drupal\Core\Render\Element\Email;
 use Drupal\Core\Form\FormStateInterface;
@@ -115,7 +114,7 @@ function email_registration_cleanup_username($name) {
   $name = ('' === $name) ? t('user') : $name;
 
   // Truncate to a reasonable size.
-  $name = (Unicode::strlen($name) > (UserInterface::USERNAME_MAX_LENGTH - 10)) ? Unicode::substr($name, 0, UserInterface::USERNAME_MAX_LENGTH - 11) : $name;
+  $name = (mb_strlen($name) > (UserInterface::USERNAME_MAX_LENGTH - 10)) ? mb_substr($name, 0, UserInterface::USERNAME_MAX_LENGTH - 11) : $name;
   return $name;
 }