Bump mini-css-extract-plugin from 2.9.2 to 2.9.4

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 2.9.2 to 2.9.4.
- [Release notes](https://github.com/webpack-contrib/mini-css-extract-plugin/releases)
- [Changelog](https://github.com/webpack/mini-css-extract-plugin/blob/main/CHANGELOG.md)
- [Commits](webpack/mini-css-extract-plugin@v2.9.2...v2.9.4)

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

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Author: dependabot[bot]