Bump .NET Core from v2.1.401 to v2.1.815
Bump .NET Core from v2.1.401 to v2.1.815

Hopefully resolves the [No usable version of the libssl was found][1] error. See [this issue][2] for details.

[1]: https://github.com/linked-data-dotnet/json-ld.net/pull/103/checks?check_run_id=2404778423#step:7:71
[2]: https://github.com/dotnet/corert/issues/7141

NuGet/json-ld.net