Update parameters in the following API docs - 3

- Collaborations
- CommMessages
- Communication channels
- Conferences
- Content exports

Test plan:
- rake doc:api
- Verify the above doc pages for parameter accuracy

Refs SIS-403

Change-Id: I5b7c7ba70ea9ddeaed148ab8ccc24436fe307373
Reviewed-on: https://gerrit.instructure.com/38681
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Duane Johnson <duane@instructure.com>
Product-Review: Duane Johnson <duane@instructure.com>
QA-Review: Jeremy Putnam <jeremyp@instructure.com>