Consolidate the docstring of the API methods into a class docstring.

Signed-off-by: Michael Price <loneviking72@gmail.com>

mayan/apps/common/api_views.py

@@ -11,6 +11,5 @@ class APIContentTypeList(generics.ListAPIView):
     """
     Returns a list of all the available content types.
     """
-
     serializer_class = ContentTypeSerializer
     queryset = ContentType.objects.order_by('app_label', 'model')