document ability to set term on course API

fixes CNVS-11743

test plan
 - api documentation should render
 - should show that term can be set on Courses

Change-Id: I136b18e507444320af4caaffbd5fb084a0af3170
Reviewed-on: https://gerrit.instructure.com/31607
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>