Bump Newtonsoft.Json in /BlogEngine/BlogEngine.Tests

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 6.0.8 to 13.0.1.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](JamesNK/Newtonsoft.Json@6.0.8...13.0.1)

---
updated-dependencies:
- dependency-name: Newtonsoft.Json
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

BlogEngine/BlogEngine.Tests/packages.config

@@ -4,5 +4,5 @@
   <package id="Microsoft.AspNet.WebApi.Client" version="5.2.3" targetFramework="net45" />
   <package id="Microsoft.AspNet.WebApi.Core" version="5.2.3" targetFramework="net45" />
   <package id="Microsoft.AspNet.WebApi.WebHost" version="5.2.3" targetFramework="net45" />
-  <package id="Newtonsoft.Json" version="6.0.8" targetFramework="net45" />
+  <package id="Newtonsoft.Json" version="13.0.1" targetFramework="net45" />
 </packages>