Bump less from 4.1.3 to 4.2.0 in /frontend

Bumps [less](https://github.com/less/less.js) from 4.1.3 to 4.2.0.
- [Release notes](https://github.com/less/less.js/releases)
- [Changelog](https://github.com/less/less.js/blob/master/CHANGELOG.md)
- [Commits](less/less.js@v4.1.3...v4.2.0)

---
updated-dependencies:
- dependency-name: less
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

frontend/package-lock.json

@@ -101,7 +101,7 @@
     "eslint-webpack-plugin": "^3.2.0",
     "html-webpack-plugin": "^5.6.0",
     "json-loader": "^0.5.7",
-    "less": "^4.1.3",
+    "less": "^4.2.0",
     "less-loader": "^11.1.0",
     "lint-staged": "^13.0.3",
     "mini-css-extract-plugin": "^2.6.1",