Restored some wrongly removed contents

Author: javiereguiluz

testing/http_authentication.rst

@@ -10,4 +10,8 @@ How to Simulate HTTP Authentication in a Functional Test
     ease testing secured applications. See :ref:`testing_logging_in_users`
     for more information about this.
 
+    If you are still using an older version of Symfony, view
+    `previous versions of this article`_ for information on how to simulate
+    HTTP authentication.
+
 .. _previous versions of this article: https://symfony.com/doc/5.0/testing/http_authentication.html