clean up calls to cached_context_grants_right?

refs: CNVS-11425

Change-Id: I0487d98b839d33a339592d312ed8ed2134c4b62e
Reviewed-on: https://gerrit.instructure.com/35528
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>