Fix dataset update in Dual line chart demo (Fixes #1250)

ChartsDemo/Classes/Demos/LineChart2ViewController.m

@@ -165,8 +165,8 @@ - (void)setDataCount:(int)count range:(double)range
         set2.drawCircleHoleEnabled = NO;
 
         NSMutableArray *dataSets = [[NSMutableArray alloc] init];
-        [dataSets addObject:set2];
         [dataSets addObject:set1];
+        [dataSets addObject:set2];
 
         LineChartData *data = [[LineChartData alloc] initWithDataSets:dataSets];
         [data setValueTextColor:UIColor.whiteColor];