[Security] Bump node-sass from 4.13.0 to 4.13.1

Bumps [node-sass](https://github.com/sass/node-sass) from 4.13.0 to 4.13.1. **This update includes a security fix.**
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](sass/node-sass@v4.13.0...v4.13.1)

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

Author: dependabot-preview[bot]