fix: removed redundant code

Author: AhtishamShahid

lms/djangoapps/instructor/views/api.py

@@ -1642,7 +1642,7 @@ def get(self, request, *args, **kwargs):
 
 def _cohorts_csv_validator(file_storage, file_to_validate):
     """
-    Verifies that the expected columns are present in the CSV` used to add users to cohorts.
+    Verifies that the expected columns are present in the CSV used to add users to cohorts.
     """
     with file_storage.open(file_to_validate) as f:
         reader = csv.reader(f.read().decode('utf-8-sig').splitlines())
@@ -4425,9 +4425,6 @@ def get(self, request, course_id):
             Response: A DRF Response object containing the serialized
                       course modes or an error.
         """
-        if not CourseOverview.objects.filter(id=course_id).exists():
-            return Response(status=status.HTTP_404_NOT_FOUND)
-
         all_modes = CourseMode.objects.filter(course_id=course_id)
 
         serializer = CourseModeSerializer(all_modes, many=True)