Update WASDK version to 1.8.260204000 to match Win2d dependency and fix build errors

Author: Arlodotexe

MultiTarget/PackageReferences/WinAppSdk.props

@@ -1,6 +1,6 @@
 <Project>
   <ItemGroup>
-    <PackageReference Condition="'$(HasWinUI)' == 'true'" Include="Microsoft.WindowsAppSDK.WinUI" Version="1.8.250906003" />
+    <PackageReference Condition="'$(HasWinUI)' == 'true'" Include="Microsoft.WindowsAppSDK.WinUI" Version="1.8.260204000" />
     <PackageReference Condition="'$(HasWinUI)' == 'true'" Include="Microsoft.Windows.CsWinRT" Version="2.2.0" PrivateAssets="all" />
     <PackageReference Condition="'$(HasWinUI)' == 'true'" Include="Microsoft.Web.WebView2" Version="1.0.3179.45" PrivateAssets="all" />
   </ItemGroup>