Update Microsoft.WindowsAppSdk to 1.6 stable

Author: Arlodotexe

MultiTarget/PackageReferences/WinAppSdk.props

@@ -1,6 +1,6 @@
 <Project>
   <ItemGroup>
-    <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.6.240821007-preview2" />
+    <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.6.240829007" />
     <PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.22621.756" />
     <PackageReference Include="Microsoft.Web.WebView2" Version="1.0.2730-prerelease" />
   </ItemGroup>