updated user_role_grants docs

[fantapop]

Previously, it was unknown that ORG_MEMBER was required to be passed. Ideally this would not be the case but as a quick fix, we update the docs and examples to indicate that it is required.

Commit checklist

• [x] Changelog
• [x] Doc gen (make generate)
• [ ] Integration test(s)
• [ ] Acceptance test(s)
• [x] Example(s)