Bump Newtonsoft.Json in /openapi-diff/src/core/OpenApiDiff.Core

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 9.0.1 to 13.0.1.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](JamesNK/Newtonsoft.Json@9.0.1...13.0.1)

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

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

Author: dependabot[bot]

openapi-diff/src/core/OpenApiDiff.Core/OpenApiDiff.Core.csproj

@@ -17,7 +17,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="System.Reflection.TypeExtensions" Version="4.3.0" />
     <PackageReference Include="YamlDotNet.Signed" Version="5.0.0" />