set privateassets for Microsoft.VisualStudio.Threading.Analyzers (#124)

Author: csdecrypt

Source/Schema.NET/Schema.NET.csproj

@@ -42,7 +42,7 @@
     <!-- See https://github.com/Microsoft/dotnet/tree/master/releases/reference-assemblies -->
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" PrivateAssets="All" Version="1.0.0" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" PrivateAssets="All" Version="1.0.0" />
-    <PackageReference Include="Microsoft.VisualStudio.Threading.Analyzers" Version="16.4.43" />
+    <PackageReference Include="Microsoft.VisualStudio.Threading.Analyzers" PrivateAssets="All" Version="16.4.43" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
     <PackageReference Include="System.Memory" Version="4.5.3" />
   </ItemGroup>