Bump sass-loader from 6.0.7 to 7.3.1

Bumps [sass-loader](https://github.com/webpack-contrib/sass-loader) from 6.0.7 to 7.3.1.
- [Release notes](https://github.com/webpack-contrib/sass-loader/releases)
- [Changelog](https://github.com/webpack-contrib/sass-loader/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/sass-loader/compare/v6.0.7...v7.3.1)

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

package.json

@@ -36,7 +36,7 @@
     "node-sass": "^4.13.0",
     "postcss-cssnext": "^3.0.2",
     "postcss-loader": "^2.0.8",
-    "sass-loader": "^6.0.6",
+    "sass-loader": "^7.3.1",
     "shx": "^0.2.2",
     "style-loader": "^0.19.0",
     "stylelint": "^8.2.0",