Bump Newtonsoft.Json in /Tests/FluentAssertions.Specs

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 11.0.2 to 13.0.2.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](JamesNK/Newtonsoft.Json@11.0.2...13.0.2)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Tests/FluentAssertions.Specs/FluentAssertions.Specs.csproj

@@ -61,7 +61,7 @@
 
   <ItemGroup>
     <PackageReference Include="Chill" Version="4.1.0" />
-    <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="Xunit.StaFact" Version="1.1.11" />
     <PackageReference Include="System.Data.DataSetExtensions" Version="4.5.0" />