Bump Newtonsoft.Json in /Demo/keyvaultdemo/mykeyvault

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 12.0.1 to 13.0.2.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](https://github.com/JamesNK/Newtonsoft.Json/compare/12.0.1...13.0.2)

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

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Demo/keyvaultdemo/mykeyvault/packages.config

@@ -18,7 +18,7 @@
   <package id="Microsoft.Rest.ClientRuntime" version="2.3.18" targetFramework="net461" />
   <package id="Microsoft.Rest.ClientRuntime.Azure" version="3.3.18" targetFramework="net461" />
   <package id="Microsoft.Win32.Primitives" version="4.3.0" targetFramework="net461" />
-  <package id="Newtonsoft.Json" version="12.0.1" targetFramework="net461" />
+  <package id="Newtonsoft.Json" version="13.0.2" targetFramework="net461" />
   <package id="System.Collections" version="4.3.0" targetFramework="net461" />
   <package id="System.Collections.Concurrent" version="4.3.0" targetFramework="net461" />
   <package id="System.Diagnostics.Debug" version="4.3.0" targetFramework="net461" />