Replace old conditional lettuce test with bok choy version.

cms/djangoapps/contentstore/views/item.py

cms/djangoapps/contentstore/views/tests/test_item.py

common/test/acceptance/fixtures/course.py

common/test/acceptance/pages/lms/conditional.py

common/test/acceptance/tests/lms/test_conditional.py

lms/djangoapps/courseware/features/conditional.feature

lms/djangoapps/courseware/features/conditional.py