Updates for 2.8! (#961)

platform_design/lib/main.dart

@@ -36,8 +36,7 @@ class MyAdaptingApp extends StatelessWidget {
           child: Material(child: child),
         );
       },
-      // ignore: use_key_in_widget_constructors, prefer_const_constructors
-      home: PlatformAdaptingHomePage(),
+      home: const PlatformAdaptingHomePage(),
     );
   }
 }