Removing 'not what you're looking for' link

Usage is negligible (0.352% of pageviews result in it being clicked) and it's a jarring experience

Related pull requests on other branches — 

alphagov/frontend/pull/512
alphagov/smart-answers/pull/700
alphagov/licence-finder/pull/51
alphagov/calendars/pull/57
alphagov/prototyping-v2/pull/1
alphagov/transaction-wrappers/pull/42