chore(deps): bump jsonwebtoken and serverless-offline in /demo/server

Removes [jsonwebtoken](https://github.com/auth0/node-jsonwebtoken). It's no longer used after updating ancestor dependency [serverless-offline](https://github.com/dherault/serverless-offline). These dependencies need to be updated together.


Removes `jsonwebtoken`

Updates `serverless-offline` from 6.9.0 to 12.0.4
- [Release notes](https://github.com/dherault/serverless-offline/releases)
- [Changelog](https://github.com/dherault/serverless-offline/blob/master/CHANGELOG.md)
- [Commits](dherault/serverless-offline@v6.9.0...v12.0.4)

---
updated-dependencies:
- dependency-name: jsonwebtoken
  dependency-type: indirect
- dependency-name: serverless-offline
  dependency-type: direct:development
...

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