[symfony#2479] Minor tweak for new debug article

Author: weaverryan

components/debug.rst

@@ -68,7 +68,7 @@ and more useful::
 
 .. note::
 
-    If the :doc:`HttpFoundation component </components/http_foundation>` is
+    If the :doc:`HttpFoundation component </components/http_foundation/introduction>` is
     available, the handler uses a Symfony Response object; if not, it falls
     back to a regular PHP response.