Build(deps-dev): Bump mini-css-extract-plugin in /frontend

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 2.9.0 to 2.9.1.
- [Release notes](https://github.com/webpack-contrib/mini-css-extract-plugin/releases)
- [Changelog](https://github.com/webpack-contrib/mini-css-extract-plugin/blob/master/CHANGELOG.md)
- [Commits](webpack-contrib/mini-css-extract-plugin@v2.9.0...v2.9.1)

---
updated-dependencies:
- dependency-name: mini-css-extract-plugin
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

frontend/package.json

@@ -27,7 +27,7 @@
     "css-loader": "^7.1.2",
     "html-webpack-plugin": "^5.6.0",
     "jest": "^27.5.1",
-    "mini-css-extract-plugin": "^2.9.0",
+    "mini-css-extract-plugin": "^2.9.1",
     "postcss": "^8.4.41",
     "postcss-loader": "^8.1.1",
     "prettier": "^3.3.3",