spec: update courses api for post policies
spec: update courses api for post policies

Change-Id: Ifbde4de9f6bd869d32065773664989993dcff18e
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/229535
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Nick Pitrak <1d88e258cca3cea49ddd3c88644b8ac147b565af@instructure.com>
QA-Review: Jeremy Neander <20252aad5efdc666f083d82ab63ed0f9f72a043e@instructure.com>
Product-Review: Jeremy Neander <20252aad5efdc666f083d82ab63ed0f9f72a043e@instructure.com>

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