Fix link to 'How to archive a Smart Answer'
Fix link to 'How to archive a Smart Answer'

Change 'docs' to 'doc' in link.
stwalsh/smart-answers,alphagov/smart-answers,alphagov/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,tadast/smart-answers,alphagov/smart-answers,askl56/smart-answers,lutgendorff/smart-answers,stwalsh/smart-answers,aledelcueto/smart-answers,lutgendorff/smart-answers,aledelcueto/smart-answers,askl56/smart-answers,tadast/smart-answers,aledelcueto/smart-answers,tadast/smart-answers,aledelcueto/smart-answers,askl56/smart-answers,tadast/smart-answers,lutgendorff/smart-answers,askl56/smart-answers,lutgendorff/smart-answers,alphagov/smart-answers