minor #12478 Update http_foundation.rst (atailouloute)

This PR was merged into the 3.4 branch.

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Update http_foundation.rst

Add immutable option to `setCache` example

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cda341d Update http_foundation.rst

Author: javiereguiluz

components/http_foundation.rst

@@ -421,6 +421,7 @@ call::
         's_maxage'      => 600,
         'private'       => false,
         'public'        => true,
+        'immutable'     => true,
     ]);
 
 To check if the Response validators (``ETag``, ``Last-Modified``) match a