perf: Exclude the definition of the CanCenterOverWPFOwnerPropertyInfo…

… field in .NET 8 or higher (#1202)

Co-authored-by: pomian <[email protected]>

src/Wpf.Ui/Controls/MessageBox/MessageBox.cs

@@ -236,10 +236,12 @@ public bool IsPrimaryButtonEnabled
     /// </summary>
     public IRelayCommand TemplateButtonCommand => (IRelayCommand)GetValue(TemplateButtonCommandProperty);
 
+#if !NET8_0_OR_GREATER
     private static readonly PropertyInfo CanCenterOverWPFOwnerPropertyInfo = typeof(Window).GetProperty(
         "CanCenterOverWPFOwner",
         BindingFlags.NonPublic | BindingFlags.Instance
     )!;
+#endif
 
     /// <summary>
     /// Initializes a new instance of the <see cref="MessageBox"/> class.