Revert the removal of LayoutUpdated_revoker from ColorSchemes in ab79a85

Author: DHowett

src/cascadia/TerminalSettingsEditor/ColorSchemes.h

@@ -13,6 +13,7 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
 {
     struct ColorSchemes : public HasScrollViewer<ColorSchemes>, ColorSchemesT<ColorSchemes>
     {
+    public:
         ColorSchemes();
 
         void OnNavigatedTo(const winrt::Windows::UI::Xaml::Navigation::NavigationEventArgs& e);
@@ -25,6 +26,9 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
         WINRT_OBSERVABLE_PROPERTY(Editor::ColorSchemesPageViewModel, ViewModel, _PropertyChangedHandlers, nullptr);
 
         WINRT_CALLBACK(PropertyChanged, Windows::UI::Xaml::Data::PropertyChangedEventHandler);
+
+    private:
+        winrt::Windows::UI::Xaml::FrameworkElement::LayoutUpdated_revoker _layoutUpdatedRevoker;
     };
 }