Fix issue with file previews hidden with "Institution" visibility
Fix issue with file previews hidden with "Institution" visibility

Fixes CNVS-33763

Test Plan:
* Prerequisite: Kaltura/Notorious plugin enabled for generating
  file previews
* Create a course with "Institution" visibility.
* Upload a media file to the course.
* Create a content page and link the media file using the sidebar.
* Log in or masquerade as a non-enrolled user.
* Access the page and see that the file link appears along
  with its preview.

Change-Id: If5590abaded4d74a1f5d737fe84de42bb60c6ffe
Reviewed-on: https://gerrit.instructure.com/97790
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
QA-Review: Heath Hales <8ca81b68c7e2592ac614bd07f22fcc735ca55f93@instructure.com>
Product-Review: Dan Minkevitch <2591e5f46f28d303f9dc027d475a5c60d8dea17a@instructure.com>

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