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>

simplistic_calculator/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -0,0 +1,12 @@
+//
+//  Generated file. Do not edit.
+//
+
+import FlutterMacOS
+import Foundation
+
+import window_size
+
+func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  WindowSizePlugin.register(with: registry.registrar(forPlugin: "WindowSizePlugin"))
+}