message: Subscribe AboutWindowViewModel to external changes of update channel (win)
diff: @@ -16,7 +16,7 @@ namespace TogglDesktop.ViewModels
  {
  VersionText = versionText;
  _updateService = updateService;
  - SelectedChannel = _updateService.UpdateChannel.Value;
  + _updateService.UpdateChannel.DistinctUntilChanged().Subscribe(channel => SelectedChannel = channel);
  this.WhenValueChanged(x => x.SelectedChannel)
  .Subscribe(_updateService.UpdateChannel.OnNext);
  var updateStatus = updateService.UpdateStatus;
  