Use block arg in SmartAnswersController#with_format
Use block arg in SmartAnswersController#with_format

This method is only ever invoked from within the `show` action of this
controller and it is always invoked with a block.

This change makes explicit use of the `block` argument to make the code more
readable while continuing to avoid violating the `Lint/UnusedMethodArgument`
cop.

aledelcueto/smart-answers,stwalsh/smart-answers,alphagov/smart-answers,alphagov/smart-answers,aledelcueto/smart-answers,alphagov/smart-answers,stwalsh/smart-answers,aledelcueto/smart-answers,aledelcueto/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,alphagov/smart-answers