chore: fix versions multitarget net6

Author: jkone27

ApiStub.FSharp/ApiStub.FSharp.fsproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <PackageId>ApiStub.FSharp</PackageId>
     <Version>1.2.5</Version>
@@ -28,11 +28,15 @@
     <Compile Include="Csharp.fs" />
     <Compile Include="BDD.fs" />
   </ItemGroup>
-  <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="8.0.15">
-      <GeneratePathProperty></GeneratePathProperty>
-    </PackageReference>
+  <ItemGroup Condition="'$(TargetFramework)' == 'net6.0'">
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="6.0.3" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="6.0.0" />
+  </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="8.0.15" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="9.0.4" />
+  </ItemGroup>
+  <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="all" />
   </ItemGroup>
   <ItemGroup>