Avoid Yard warning messages
Avoid Yard warning messages

closes OUT-2130

test plan:
  - confirm no warnings appear when generating docs:
    > docker-compose run --rm web bundle exec rake doc:api

Change-Id: I39b0bbf51de7b581ce133ebdc95db2f3048d967a
Reviewed-on: https://gerrit.instructure.com/172820
Tested-by: Jenkins
Reviewed-by: Neil Gupta <cc4fec8a34766005dd45d48be045c08d736c11ed@instructure.com>
Reviewed-by: Matthew Berns <e53c8988cd428dde240324ce2797c8eb7073560f@instructure.com>
QA-Review: Matthew Berns <e53c8988cd428dde240324ce2797c8eb7073560f@instructure.com>
Product-Review: Augusto Callejas <7d9b9fd126d23d111f693e51511b33ea0e7192f6@instructure.com>

instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms