Update sass-loader requirement from 7.1.0 to 7.3.1

Updates the requirements on [sass-loader](https://github.com/webpack-contrib/sass-loader) to permit the latest version.
- [Release notes](https://github.com/webpack-contrib/sass-loader/releases)
- [Changelog](https://github.com/webpack-contrib/sass-loader/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/sass-loader@v7.1.0...v7.3.1)

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

Author: dependabot-preview[bot]

package.json

@@ -63,7 +63,7 @@
     "mini-css-extract-plugin": "0.5.0",
     "node-sass": "4.11.0",
     "optimize-css-assets-webpack-plugin": "5.0.1",
-    "sass-loader": "7.1.0",
+    "sass-loader": "7.3.1",
     "style-loader": "0.23.1",
     "webpack": "4.29.6",
     "webpack-cli": "3.3.0",