chore: Update jsonschema to 0.28.0

[Stranger6667]

This PR updates jsonschema to 0.28.0 and makes use of its newer APIs.

[danieldk]

Thanks! The version bumps seem to cause issues elsewhere: https://github.com/huggingface/text-generation-inference/actions/runs/12686931224/job/35360265368?pr=2893#step:7:1626

[Stranger6667]

Thanks @danieldk

Let me look into it

[Stranger6667]

Hm, reqwest does not have the blocking feature enabled, even though the blocking submodule enabled by this feature is explicitly used in validation.rs:539

[Stranger6667]

I pushed a commit that adds blocking to reqwest, this should pass now. Sorry for not checking it earlier!