Point to the proper AppConfig in INSTALLED_APPS for course_modes.

cms/envs/common.py

@@ -988,7 +988,7 @@ INSTALLED_APPS = [
     'django.contrib.admin',
 
     # for managing course modes
-    'course_modes',
+    'course_modes.apps.CourseModesConfig',
 
     # Verified Track Content Cohorting (Beta feature that will hopefully be removed)
     'openedx.core.djangoapps.verified_track_content',

lms/envs/common.py

@@ -2159,7 +2159,7 @@ INSTALLED_APPS = [
     'notifier_api',
 
     # Different Course Modes
-    'course_modes',
+    'course_modes.apps.CourseModesConfig',
 
     # Enrollment API
     'enrollment',