chore(deps-dev): bump postcss-nested from 4.1.2 to 4.2.1

Bumps [postcss-nested](https://github.com/postcss/postcss-nested) from 4.1.2 to 4.2.1.
- [Release notes](https://github.com/postcss/postcss-nested/releases)
- [Changelog](https://github.com/postcss/postcss-nested/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss-nested/compare/4.1.2...4.2.1)

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

package.json

@@ -29,7 +29,7 @@
     "babel-preset-react-app": "^9.0.2",
     "cypress": "^3.5.0",
     "husky": "^3.0.9",
-    "postcss-nested": "^4.1.2",
+    "postcss-nested": "^4.2.1",
     "prettier": "1.18.2",
     "prop-types": "^15.7.2",
     "react": "^16.11.0",