remove $(NetFrameworkCurrent) from test project

Author: jonsequitur

src/System.CommandLine.Tests/System.CommandLine.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>$(NetMinimum);$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(TargetFrameworkForNETSDK)</TargetFrameworks>
     <GenerateProgramFile>false</GenerateProgramFile>
     <DefaultExcludesInProjectFolder>$(DefaultExcludesInProjectFolder);TestApps\**</DefaultExcludesInProjectFolder>
     <NoWarn>$(NoWarn);CS8632</NoWarn> <!-- Suppress nullable warning for files included as links -->