Update deprecated method

Author: nohli

example/test/android_id_example_test.dart

@@ -16,11 +16,12 @@ void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
   setUp(() {
-    channel.setMockMethodCallHandler((MethodCall methodCall) async => '42');
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+        .setMockMethodCallHandler(channel, (MethodCall methodCall) async => '42');
   });
 
   tearDown(() {
-    channel.setMockMethodCallHandler(null);
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMethodCallHandler(channel, null);
   });
 
   testWidgets('Gets and displays Android ID', (WidgetTester tester) async {

test/android_id_test.dart

@@ -9,11 +9,12 @@ void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
   setUp(() {
-    channel.setMockMethodCallHandler((MethodCall methodCall) async => '42');
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+        .setMockMethodCallHandler(channel, (MethodCall methodCall) async => '42');
   });
 
   tearDown(() {
-    channel.setMockMethodCallHandler(null);
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMethodCallHandler(channel, null);
   });
 
   test('getAndroidId', () async {