Fix #consultation_header_title helper.
Fix #consultation_header_title helper.

Although the method was working with the @document instance variable I'm
fairly sure that wasn't the original intention.

robinwhittleton/whitehall,hotvulcan/whitehall,ggoral/whitehall,ggoral/whitehall,ggoral/whitehall,hotvulcan/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,YOTOV-LIMITED/whitehall,askl56/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,robinwhittleton/whitehall,alphagov/whitehall,alphagov/whitehall,hotvulcan/whitehall,alphagov/whitehall,askl56/whitehall,askl56/whitehall,askl56/whitehall,robinwhittleton/whitehall