Refactor conditions option for associations to fix typo and get GPA back to 4.0

Code Climate complex method warning: https://codeclimate.com/github/pjc/learn_rails/LearnRails::Associations?from_sha=99998731&to_sha=6add8dd7

Closing `}` is missing: https://github.com/pjc/learn_rails/blob/master/features/associations.feature#L200