Update webpack-cli requirement from 3.1.2 to 3.2.1 (#3850)

Updates the requirements on [webpack-cli](https://github.com/webpack/webpack-cli) to permit the latest version.
- [Release notes](https://github.com/webpack/webpack-cli/releases)
- [Changelog](https://github.com/webpack/webpack-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-cli/commits

)

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