Bump json-schema from 0.2.3 to 0.4.0 in /tests/performance

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

)

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

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

For https://github.com/turt2live/matrix-media-repo/issues/365

Add users' usage statistics (admin) API endpoint