Bump Newtonsoft.Json in /Samples/FireSharp.Sample.Windows8App

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] <support@github.com>

Author: dependabot[bot]

Samples/FireSharp.Sample.Windows8App/packages.config

@@ -5,5 +5,5 @@
   <package id="Microsoft.Bcl.Async" version="1.0.168" targetFramework="win81" />
   <package id="Microsoft.Bcl.Build" version="1.0.21" targetFramework="win81" />
   <package id="Microsoft.Net.Http" version="2.2.29" targetFramework="win81" />
-  <package id="Newtonsoft.Json" version="6.0.8" targetFramework="win81" />
+  <package id="Newtonsoft.Json" version="13.0.1" targetFramework="win81" />
 </packages>