Ignore courses on Trash when considering tasks for Sensei Home

[fjorgemota]

Right now, when the tasks query the database, we don't ignore trashed posts. However, those must be ignored, because the items there are deleted after 30 days by default anyway.

We should add that filter for all the tasks that query on the courses created by the user:

• [ ] Create your First Course;
• [ ] Publish your First Course;