[Windows] Remove TODONE (#51005)

This TODO is TODONE!

Part of flutter/flutter#131616

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: loic-sharma

shell/platform/windows/windows_lifecycle_manager.cc

@@ -192,9 +192,6 @@ void WindowsLifecycleManager::BeginProcessingExit() {
   process_exit_ = true;
 }
 
-// TODO(schectman): Wait until the platform channel is registered to send
-// the platform message.
-// https://github.com/flutter/flutter/issues/131616
 void WindowsLifecycleManager::SetLifecycleState(AppLifecycleState state) {
   if (state_ == state) {
     return;