chore(deps-dev): bump eslint from 6.6.0 to 6.7.1 in /core

Bumps [eslint](https://github.com/eslint/eslint) from 6.6.0 to 6.7.1.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v6.6.0...v6.7.1)

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