Fix Test TFM

Author: caigen

GraphLayout/Test/MSAGLTests/MSAGLTests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0-windows</TargetFramework>
+    <TargetFramework>net8.0-windows</TargetFramework>
     <LangVersion>latest</LangVersion>
 
     <AssemblyName>Microsoft.Msagl.UnitTests</AssemblyName>

GraphLayout/Test/TestGraphmaps/TestGraphmaps.csproj

@@ -4,7 +4,7 @@
 		<OutputType>WinExe</OutputType>
 		<RootNamespace>TestGraphmaps</RootNamespace>
 		<AssemblyName>TestGraphmaps</AssemblyName>
-		<TargetFrameworks>net6.0-windows</TargetFrameworks>
+		<TargetFrameworks>net8.0-windows</TargetFrameworks>
 		<UseWPF>true</UseWPF>
 		<NoWarn>CS8618;CS8603</NoWarn>