Merge pull request #1025 from dotnet/dev/jmarolf/json-library-load-error

Fix Microsoft.CodeAnalysis.Analyzer.Testing nuget package dependencies for downstream clients

src/Microsoft.CodeAnalysis.Testing/Directory.Build.props

@@ -84,7 +84,7 @@
 
   <!-- Needed to override the transitive 9.0.1 version brought in by the 16.1.1 Microsoft.NET.Test.Sdk -->
   <ItemGroup>
-    <PackageReference Include="Newtonsoft.Json" Version="$(NewtonsoftJsonVersion)" />
+    <PackageReference Include="Newtonsoft.Json" Version="$(NewtonsoftJsonVersion)" ExcludeAssets="all" />
   </ItemGroup>
 
   <!-- Use a different versioning scheme for nuget packages -->

src/Microsoft.CodeAnalysis.Testing/Microsoft.CodeAnalysis.Analyzer.Testing/Microsoft.CodeAnalysis.Analyzer.Testing.csproj

@@ -31,7 +31,7 @@
     </When>
     <Otherwise>
       <PropertyGroup>
-        <NuGetApiVersion>5.6.0</NuGetApiVersion>
+        <NuGetApiVersion>6.3.0</NuGetApiVersion>
       </PropertyGroup>
     </Otherwise>
   </Choose>

tests/Microsoft.CodeAnalysis.Testing/Directory.Build.props

@@ -21,7 +21,7 @@
   <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../'))" />
 
   <PropertyGroup>
-    <TestTargetFrameworks>netcoreapp3.1;net472;net46</TestTargetFrameworks>
+    <TestTargetFrameworks>netcoreapp3.1;net472</TestTargetFrameworks>
     <SourceGeneratorTestTargetFrameworks>netcoreapp3.1;net472</SourceGeneratorTestTargetFrameworks>
 
     <!-- Workaround dependencies that do not yet support netcoreapp3.1 https://github.com/dotnet/roslyn/issues/45114 -->