feat: update flutter to 3.24.6 (#1336)

ui/flutter/windows/runner/main.cpp

@@ -65,11 +65,6 @@ int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
 
   flutter::DartProject project(L"data");
 
-  // TODO: Remove this.
-  // This forces Flutter to use a separate thread for Dart.
-  // This mode will be removed in a future version of Flutter.
-  project.set_ui_thread_policy(flutter::UIThreadPolicy::RunOnSeparateThread);
-
   std::vector<std::string> command_line_arguments =
       GetCommandLineArguments();