update rubric criteria api docs

Some properties were missing

Test Plan:
 * RubricCriteria object description should have outcome_id/vendor_guid/long_description

closes PLAT-811

Change-Id: I5a5d264c49a4d7ad6406e2574b5c3e6c69683ee9
Reviewed-on: https://gerrit.instructure.com/46196
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Bracken Mosbacker <bracken@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>