Changed Sample Target Version to Latest .NET9 Target Version.

Author: SowntharyaJ

ChatApplication/ChatApplication/ChatApplication.csproj

@@ -60,7 +60,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<PackageReference Include="Microsoft.Maui.Controls" Version="9.0.21" />
+		<PackageReference Include="Microsoft.Maui.Controls" Version="$(MauiVersion)" />
 		<PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="9.0.0" />
 		<PackageReference Include="Syncfusion.Maui.ListView" Version="*" />
 	</ItemGroup>