chore(deps-frontend):(deps): bump mini-css-extract-plugin in /frontend

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 2.9.3 to 2.9.4.
- [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/mini-css-extract-plugin@v2.9.3...v2.9.4)

---
updated-dependencies:
- dependency-name: mini-css-extract-plugin
  dependency-version: 2.9.4
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]