chore(deps-dev): bump ajv from 6.12.6 to 6.15.0 (#3033)

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.12.6 to 6.15.0.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.12.6...v6.15.0)

---
updated-dependencies:
- dependency-name: ajv
  dependency-version: 6.14.0
  dependency-type: indirect
...

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