Bump validator in /samples/EventGridIntegration/javascript (#320)

Bumps [validator](https://github.com/validatorjs/validator.js) from 13.12.0 to 13.15.20.
- [Release notes](https://github.com/validatorjs/validator.js/releases)
- [Changelog](https://github.com/validatorjs/validator.js/blob/master/CHANGELOG.md)
- [Commits](validatorjs/validator.js@13.12.0...13.15.20)

---
updated-dependencies:
- dependency-name: validator
  dependency-version: 13.15.20
  dependency-type: indirect
...

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