Remove track-changes-discount experiment

services/web/public/coffee/main/account-upgrade.coffee

@@ -9,10 +9,9 @@ define [
 			event_tracking.sendMB "subscription-start-trial", { source, plan: $scope.startTrialPlanCode }
 
 			w = window.open()
-			sixpack.convert "track-changes-discount", ->
-				ga?('send', 'event', 'subscription-funnel', 'upgraded-free-trial', source)
-				url = "/user/subscription/new?planCode=#{$scope.startTrialPlanCode}&ssp=true"
-				if couponCode?
-					url = "#{url}&cc=#{couponCode}"
-				$scope.startedFreeTrial = true
-				w.location = url
+			ga?('send', 'event', 'subscription-funnel', 'upgraded-free-trial', source)
+			url = "/user/subscription/new?planCode=#{$scope.startTrialPlanCode}&ssp=true"
+			if couponCode?
+				url = "#{url}&cc=#{couponCode}"
+			$scope.startedFreeTrial = true
+			w.location = url