Bump is-my-json-valid from 2.15.0 to 2.20.0

Bumps [is-my-json-valid](https://github.com/mafintosh/is-my-json-valid) from 2.15.0 to 2.20.0.
- [Release notes](https://github.com/mafintosh/is-my-json-valid/releases)
- [Commits](mafintosh/is-my-json-valid@v2.15.0...v2.20.0)

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Author: dependabot[bot]