fix: primitive delete in tabs test

now dates is the last element of ithe list and progress is always before dates.(penultimate)

cms/djangoapps/contentstore/views/tests/test_tabs.py

@@ -191,7 +191,7 @@ def test_delete(self):
             tabs.primitive_delete(course, 6)
 
         assert course.tabs[1] != {'type': 'dates', 'name': 'Dates'}
-        tabs.primitive_delete(course, 1)
+        tabs.primitive_delete(course, -2)
         assert {'type': 'progress'} not in course.tabs
         # Check that dates has shifted up
         assert course.tabs[1] == {'type': 'dates', 'name': 'Dates'}