Fix typehint for Exception::responseHeader().
Fix typehint for Exception::responseHeader().

cakephp/cakephp,ndm2/cakephp,cakephp/cakephp,ndm2/cakephp,cakephp/cakephp,CakeDC/cakephp,CakeDC/cakephp,ADmad/cakephp,CakeDC/cakephp,dakota/cakephp,ADmad/cakephp,cakephp/cakephp,ADmad/cakephp,ndm2/cakephp,dakota/cakephp,dakota/cakephp,dakota/cakephp,ADmad/cakephp,CakeDC/cakephp,ndm2/cakephp