Update for Flutter 3.10 beta (#1746)

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] All existing and new tests are passing.

---------

Co-authored-by: David Iglesias <ditman@gmail.com>
Co-authored-by: Mark Thompson <2554588+MarkTechson@users.noreply.github.com>
Co-authored-by: John Ryan <ryjohn@google.com>

experimental/material_3_demo/lib/main.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'package:flutter/material.dart';
-import 'package:flutter/scheduler.dart';
 
 import 'constants.dart';
 import 'home.dart';
@@ -32,7 +31,7 @@ class _AppState extends State<App> {
   bool get useLightMode {
     switch (themeMode) {
       case ThemeMode.system:
-        return SchedulerBinding.instance.window.platformBrightness ==
+        return View.of(context).platformDispatcher.platformBrightness ==
             Brightness.light;
       case ThemeMode.light:
         return true;