Fix the showing floating value in bar chart sample1 (#2011)

Author: imaNNeo

example/lib/presentation/samples/bar/bar_chart_sample1.dart

@@ -202,7 +202,7 @@ class BarChartSample1State extends State<BarChartSample1> {
               ),
               children: <TextSpan>[
                 TextSpan(
-                  text: (rod.toY - 1).toString(),
+                  text: ((rod.toY - 1).toStringAsFixed(1)).toString(),
                   style: const TextStyle(
                     color: Colors.white, //widget.touchedBarColor,
                     fontSize: 16,