Removed duplicate code

common/djangoapps/terrain/course_helpers.py

@@ -66,21 +66,6 @@ def add_to_course_staff(username, course_num):
 
 
 @world.absorb
-def add_to_course_staff(username, course_num):
-    """
-    Add the user with `username` to the course staff group
-    for `course_num`.
-    """
-    # Based on code in lms/djangoapps/courseware/access.py
-    group_name = "instructor_{}".format(course_num)
-    group, _ = Group.objects.get_or_create(name=group_name)
-    group.save()
-
-    user = User.objects.get(username=username)
-    user.groups.add(group)
-
-
-@world.absorb
 def clear_courses():
     # Flush and initialize the module store
     # Note that if your test module gets in some weird state