Fixed criterion name with label which is displayed to the user.

Ticket: [TNL-768] (https://openedx.atlassian.net/browse/TNL-768)

Field "label" added in "Criterion" model but not updated in "staff_debug_info.html" template. It was showing a unique identifier for new criterion and if we change the name of default criterion then it shows its default name but not updated name which is stored in "label" field.