Remove/update comments related to django 1.4

Course keys as PKs don't appear to break detail links in admin pages
anymore.

openedx/core/djangoapps/content/course_overviews/admin.py

@@ -12,16 +12,6 @@ from .models import CourseOverview, CourseOverviewImageConfig, CourseOverviewIma
 class CourseOverviewAdmin(admin.ModelAdmin):
     """
     Simple, read-only list/search view of Course Overviews.
-
-    The detail view is broken because our primary key for this model are
-    course keys, which can have a number of chars that break admin URLs.
-    There's probably a way to make this work properly, but I don't have the
-    time to investigate. I would normally disable the links by setting
-    `list_display_links = None`, but that's not a valid value for that
-    field in Django 1.4. So I'm left with creating a page where the detail
-    view links are all broken for Split courses. Because I only created
-    this page to manually test a hotfix, the list view works for this
-    purpose, and that's all the yak I have time to shave today.
     """
     list_display = [
         'id',

openedx/core/djangoapps/content/course_overviews/tests/test_course_overviews.py

@@ -355,11 +355,10 @@ class CourseOverviewTestCase(ModuleStoreTestCase):
                 'openedx.core.djangoapps.content.course_overviews.models.CourseOverview._get_pk_val'
             ) as mock_get_pk_val:
                 mock_get_pk_val.return_value = None
-                # This method was not present in django 1.4. Django 1.8 calls this method if
-                # _get_pk_val returns None.  This method will return empty str if there is no
-                # default value present. So mock it to avoid returning the empty str as primary key
-                # value. Due to empty str, model.save will do an update instead of insert which is
-                # incorrect and get exception in
+                # Django 1.8+ calls this method if _get_pk_val returns None.  This method will
+                # return empty str if there is no default value present. So mock it to avoid
+                # returning the empty str as primary key value. Due to empty str, model.save will do
+                # an update instead of insert which is incorrect and get exception in
                 # openedx.core.djangoapps.xmodule_django.models.OpaqueKeyField.get_prep_value
                 with mock.patch('django.db.models.Field.get_pk_value_on_save') as mock_get_pk_value_on_save: