Allow Student to Withdraw their Request a Change submission

[HRAGANBC]

User Story As a student, I want to be able to withdraw my submitted Request a Change, so that if I submitted incorrect information accidentally, I don't have to wait the standard processing times for it to be denied before I can re-submit a new one.

Acceptance Criteria:

• [ ] Enable ability for student to withdraw a 'Pending' Request a Change submission
• [ ] Use of this withdraw function would eliminate the request altogether (similar to deleting a draft application)