Teacher plan moment (#3816)
Teacher plan moment (#3816)

* clean models/task-plans/teacher/plan.ts model of moment.js references

* update teacher task-plan

* :shirt:

Co-authored-by: Dante Soares <40e680453dd5b9a55fd5e44db0ce04328d6a9241@rice.edu>
openstax/tutor-js,openstax/tutor-js,openstax/tutor-js,openstax/tutor-js,openstax/tutor-js