Merge pull request #7343 from AvaloniaUI/fixes/6930-sync-context-priority

Reduce the priority in AvaloniaSynchronizationContext.

src/Avalonia.Base/Threading/AvaloniaSynchronizationContext.cs

@@ -30,7 +30,7 @@ namespace Avalonia.Threading
         /// <inheritdoc/>
         public override void Post(SendOrPostCallback d, object? state)
         {
-           Dispatcher.UIThread.Post(() => d(state), DispatcherPriority.Send);
+           Dispatcher.UIThread.Post(() => d(state), DispatcherPriority.Background);
         }
 
         /// <inheritdoc/>