cpc no longer required in all setups

Author: vladimanaev

src/main/java/com/taboola/backstage/model/media/campaigns/Campaign.java

@@ -38,7 +38,6 @@ public class Campaign {
     @Required
     protected String brandingText;
     protected String trackingCode;
-    @Required
     protected Double cpc;
     protected Double dailyCap;
     protected DailyAdDeliveryModel dailyAdDeliveryModel;