Removed unused code (optionalCost);

Mage/src/main/java/mage/game/stack/StackAbility.java

@@ -381,15 +381,6 @@ public class StackAbility extends StackObjImpl implements Ability {
         }
     }
 
-    @Override
-    public Costs<Cost> getOptionalCosts() {
-        throw new UnsupportedOperationException("Not supported yet.");
-    }
-
-    @Override
-    public void addOptionalCost(Cost cost) {
-    }
-
     @Override
     public boolean checkIfClause(Game game) {
         return true;