hide "Message students" option for students
hide "Message students" option for students

test plan:
1. Have an appointment group calendar event set up
2. As a student sign up for the event
3. As the student go to the scheduler tab
4. Click on the group appointment
5. The modal that appears should have "Un-reserve" but not
   "Message students"

fixes CNVS-33550

Change-Id: Id6596d51a9d57f5bffe39078b61ca6c35596db9f
Reviewed-on: https://gerrit.instructure.com/96252
Tested-by: Jenkins
Reviewed-by: Felix Milea-Ciobanu <9384aa226ac9d3237ed0bc52e18ffcb251ee0bf7@instructure.com>
QA-Review: Deepeeca Soundarrajan <5bcd4b623f00b7fc2942cd1c65c245b30a48a61f@instructure.com>
Product-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>

sfu/canvas-lms,venturehive/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,matematikk-mooc/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,SwinburneOnline/canvas-lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,SwinburneOnline/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms