A teacher can allow notes in an Advanced uploading of files assignment

1. Login as a teacher, update an Advanced uploading of files assignment and set 'Allow notes' to Yes.
2. Login as a student and access the assignment.
3. Click the 'Edit' button, add some notes, then click the 'Save changes' button.
4. Click the 'Edit' button again, edit the text, then click the 'Save changes' button.
5. Check that the changes have been saved.