Bump ajv from 6.12.6 to 8.12.0

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.12.6 to 8.12.0.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.12.6...v8.12.0)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -35,7 +35,7 @@
  "url": "https://github.com/http-tests/cache-tests.git"
  },
  "devDependencies": {
- "ajv": "^6.12.5",
+ "ajv": "^8.12.0",
  "font-awesome": "^4.7.0",
  "standard": "^17.1.0"
  }