message: API: Simplify lecture deletion success unit test
diff: @@ -106,16 +106,11 @@ describe('Lecture', () => {
  return await testHelper.commonUserDeleteRequest(user, `/${lecture.id}`);
  }
  - it('should delete a lecture by course admin', async () => {
  + it('should delete a lecture', async () => {
  const setup = await lectureSuccessTestSetup();
  const res = await lectureDeleteTest(setup);
  res.status.should.be.equal(200);
  -
  - const {course, lecture} = setup;
  - const courseWithDeletedLecture = await Course.findById(course.id);
  - courseWithDeletedLecture.lectures[0].should.not.be.equal(lecture.id);
  - const deletedLecture = await Lecture.findById(lecture.id);
  - should.not.exist(deletedLecture, 'Lecture still exists');
  + should.not.exist(await Lecture.findById(setup.lecture.id), 'Lecture still exists');
  });
  it('should forbid lecture deletions for an unauthorized teacher', async () => {
  