Under the Administration tab navigate to-> Notifications-> Activity Associations.
Select the Show Filter button in the top right hand corner and set the Object Type to Change Order Workflow Task and the Symbol to Status.
Select the Status Symbol and on the next window select Edit in the top right hand corner.
The Activity Type should be set to Update Status, set this to <empty> and click Save.
Now when the status of a Change Order Workflow Task changes a notification should not be sent out.