Update Tests to .NET 9

Author: enisn

test/InputKit.Maui.Test/InputKit.Maui.Test.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
     <!--<TargetFrameworks>net6.0;net6.0-android;net6.0-ios;net6.0-maccatalyst;net6.0-windows10.0.19041</TargetFrameworks>-->
     <ImplicitUsings>enable</ImplicitUsings>
     <UseMaui>true</UseMaui>