change page navigation

lib/pages/invoice/payment_page.dart

@@ -8,6 +8,7 @@ import 'package:fcs/pages/widgets/multi_img_file.dart';
 import 'package:fcs/pages/widgets/my_data_table.dart';
 import 'package:fcs/pages/widgets/number_cell.dart';
 import 'package:fcs/pages/widgets/progress.dart';
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_icons/flutter_icons.dart';
 import 'package:font_awesome_flutter/font_awesome_flutter.dart';
@@ -66,7 +67,7 @@ class _PaymentPageState extends State<PaymentPage> {
         appBar: AppBar(
           centerTitle: true,
           leading: new IconButton(
-            icon: new Icon(Icons.close),
+            icon: new Icon(CupertinoIcons.back),
             onPressed: () => Navigator.of(context).pop(),
           ),
           backgroundColor: primaryColor,