[Flutter] AppBar 뒤로가기 버튼 없애기

1. automaticallyImplyLeading값을 false로 설정

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        automaticallyImplyLeading: false,
        title: const Text('Second Screen'),
      ),
      body: Container();
 	),
 }