Bump Newtonsoft.Json in /Chapter2_WPF_Controls/Exercise3.Tests

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 12.0.3 to 13.0.1.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](JamesNK/Newtonsoft.Json@12.0.3...13.0.1)

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

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Author: dependabot[bot]

Chapter2_WPF_Controls/Exercise3.Tests/packages.config

@@ -3,7 +3,7 @@
   <package id="Guts.Client" version="3.0.0" targetFramework="net472" />
   <package id="Guts.Client.Shared" version="3.0.0" targetFramework="net472" />
   <package id="Microsoft.AspNet.WebApi.Client" version="5.2.7" targetFramework="net461" />
-  <package id="Newtonsoft.Json" version="12.0.3" targetFramework="net472" />
+  <package id="Newtonsoft.Json" version="13.0.1" targetFramework="net472" />
   <package id="NUnit" version="3.12.0" targetFramework="net461" />
   <package id="NUnit3TestAdapter" version="3.17.0" targetFramework="net472" />
 </packages>