There's no need to delete your course if it's still in progress. Courses in development haven't been released yet. Only those who have a direct link to your course will be able to see it.
You can delete a repository on GitHub if you want to eliminate a course regardless of who can or cannot see it. This will delete the course from the DataCamp system entirely. It's important to note that this action cannot be reversed.
Note: A 404 error notice will appear if someone clicks on a link to a removed course.