Errors shouldn't block receiving fact check

www.agileplannerapp.com/boards/173808/cards/5005

the edition mentioned in the story had invalid links in one of its parts. errors were causing it to remain in 'fact_check' even after calling event 'receive_fact_check'.

it seems unnecessary to validate the document when we're receiving fact check response, hence this change.
What's the false argument doing here? I can't see any reference to parameters for events in the state_machine docs.