Fix editing comment updates the comment visibility (#4005)

Editing a comment which is for internal team changes it's visibility to
applicant + staff

How to reproduce:
- Login as staff
- Add a comment and then edit the same comment
- Refresh the page and see the visibility becomes Applicant + staff

When editing the comment, I didn't see staff getting a UI to update the
visibility so not allowing the visibility change in the commit edit api
seems to be the right thing to do as well