Update node-sass requirement to ~4.9.0 in /build

Updates the requirements on [node-sass](https://github.com/sass/node-sass) to permit the latest version.
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sass/node-sass/commits/v4.9.0

)

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