Merge branch '4.4'

* 4.4:
  Update http_foundation.rst

Author: javiereguiluz

components/http_foundation.rst

@@ -465,6 +465,7 @@ call::
         's_maxage'      => 600,
         'private'       => false,
         'public'        => true,
+        'immutable'     => true,
     ]);
 
 To check if the Response validators (``ETag``, ``Last-Modified``) match a