Flutter, the textTheme property of the AppBarTheme class is deprecated, what should I use instead?

I am curently learning Flutter on the Maximilian Udemy Course, and when I reached the section when I have to use the textTheme property of the AppBarTheme class, it's telling me that it's deprecated. What should I replace it with. Here is what im trying to do:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Personal Expenses',
      theme: ThemeData(
        primarySwatch: Colors.purple,
        accentColor: Colors.amber,
        fontFamily: 'Quicksand',
        appBarTheme: AppBarTheme(
          textTheme: ThemeData.light().textTheme.copyWith(
                headline6: TextStyle(
                  fontFamily: 'OpenSans',
                  fontSize: 20,
                ),
              ),
        ),
      ),
      home: MyHomePage(),
    );
  }
}

Use colorScheme instead of accentColor and titleTextStyle and toolbarTextStyle instead of textTheme

   colorScheme: Theme.of(context).colorScheme.copyWith(
              secondary: Colors.amber,
            ),

theme: ThemeData(
  primarySwatch: Colors.purple,
  colorScheme: Theme.of(context).colorScheme.copyWith(
        secondary: Colors.amber,
      ),
  fontFamily: 'Quicksand',
  appBarTheme: AppBarTheme(
    titleTextStyle: TextStyle(),
    toolbarTextStyle: TextStyle(),
  ),
),
home: MyHomePage(),

More about using themes