build(deps): bump json-schema and jsprim in /demo

Bumps [json-schema](https://github.com/kriszyp/json-schema) and [jsprim](https://github.com/joyent/node-jsprim). These dependencies needed to be updated together.

Updates `json-schema` from 0.2.3 to 0.4.0
- [Release notes](https://github.com/kriszyp/json-schema/releases)
- [Commits](kriszyp/json-schema@v0.2.3...v0.4.0)

Updates `jsprim` from 1.4.1 to 1.4.2
- [Release notes](https://github.com/joyent/node-jsprim/releases)
- [Changelog](https://github.com/TritonDataCenter/node-jsprim/blob/v1.4.2/CHANGES.md)
- [Commits](TritonDataCenter/node-jsprim@v1.4.1...v1.4.2)

---
updated-dependencies:
- dependency-name: json-schema
  dependency-type: indirect
- dependency-name: jsprim
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]