Explicitly use SmartdownAdaptor module, or app Presenters get used

See https://github.com/alphagov/smart-answers/pull/1104.

I think this covers all cases in SmartdownAdaptor. The more robust fix is
to move the app presenters into a module (likely in lib/smart_answer), which is
on a tech debt list. This unbreaks certain questions on preview
Merge pull request #1113 from alphagov/smartdown-adapter-module-fixes

Explicitly use SmartdownAdaptor module, or app Presenters get used