有没有办法在flutter中去除条形图中的这些线条？

import 'package:flutter/material.dart';

class CustomBarChart extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: _BarChartPainter(),
    );
  }
}

class _BarChartPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    // 绘制背景
    Paint backgroundPaint = Paint()..color = Colors.grey[200];
    canvas.drawRect(Offset.zero & size, backgroundPaint);

    // 绘制条形
    Paint barPaint = Paint()
      ..color = Colors.blue
      ..style = PaintingStyle.fill;
    canvas.drawRect(Rect.fromLTWH(50, 50, 100, 200), barPaint);
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return false;
  }
}