Bump Newtonsoft.Json in /Assets/Plugins/JsonSubTypes/JsonSubTypes

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](https://github.com/JamesNK/Newtonsoft.Json/compare/12.0.3...13.0.1

)

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

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