Set request stateless only if the attribute is not defined

Author: alamirault

reference/configuration/security.rst

@@ -1006,7 +1006,8 @@ the session must not be used when authenticating users:
             // ...
         };
 
-Routes under this firewall will be :ref:`configured stateless <stateless-routing>`.
+Routes under this firewall will be :ref:`configured stateless <stateless-routing>`
+when they are not explicitly configured stateless or not.
 
 .. versionadded:: 6.3