allow non-admin teachers to get user profiles

fixes CNVS-8913

test plan:
  - as a non-admin teacher
      - request student profile from api (users/:id/profile)
        - see that it works for your students
        - not for others though
  - as an admin
      - request student profile from api (users/:id/profile)
      - see that it works
  - as a student
    - go to profile page, see that it works
    - go to another students profile, see that it doesnt
    - request profile from api (users/:id/profile) see that
      it works the same

Change-Id: Ic4b32bfa3beecf23ac95c75c948880306ef55d60
Reviewed-on: https://gerrit.instructure.com/45230
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Adam Stone <astone@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>