Merge pull request #1022 from drewnoakes/upgrade-newtonsoft

Bump Newtonsoft.Json in response to security advisory

Author: drewnoakes

src/NetMQ.Tests/NetMQ.Tests.csproj

@@ -40,7 +40,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
-    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="xunit" Version="2.4.2-pre.13" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
   </ItemGroup>