Resolve #3502882 "Bc classloader"

Closes #3502882

core/includes/bootstrap.inc

@@ -44,11 +44,6 @@
  */
 define('DRUPAL_ROOT', dirname(__DIR__, 2));
 
-/**
- * Keep backward compatibility for sites with references to TranslationWrapper.
- */
-class_alias(TranslatableMarkup::class, '\Drupal\Core\StringTranslation\TranslationWrapper', TRUE);
-
 /**
  * Translates a string to the current language or to a given language.
  *