[WPF] Dont set Slider.Value if it already matches control (#9847)

Xamarin.Forms.Platform.WPF/Renderers/SliderRenderer.cs

@@ -60,6 +60,7 @@ namespace Xamarin.Forms.Platform.WPF
 
 		void HandleValueChanged(object sender, RoutedPropertyChangedEventArgs<double> routedPropertyChangedEventArgs)
 		{
+			if (Control.Value != Element.Value)
 				((IElementController)Element).SetValueFromRenderer(Slider.ValueProperty, Control.Value);
 		}