fix documentation for enroll_me when creating a course via the api

fixes CNVS-13681

test plan:
  - generate the api documentation
  - view the documentation for creating a course
  - the enroll_me option should be just enroll_me instead of course[enroll_me]
  - confirm that creating a course via the endpoint works with the enroll_me
    param not being nested under the the course param

Change-Id: Ibe46869e6642b1eeb130899f1c35571ca26c6163
Reviewed-on: https://gerrit.instructure.com/36633
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>