Bump clean-css from 3.4.27 to 4.2.4

Bumps [clean-css](https://github.com/clean-css/clean-css) from 3.4.27 to 4.2.4.
- [Release notes](https://github.com/clean-css/clean-css/releases)
- [Changelog](https://github.com/clean-css/clean-css/blob/v4.2.4/History.md)
- [Commits](clean-css/clean-css@v3.4.27...v4.2.4)

---
updated-dependencies:
- dependency-name: clean-css
  dependency-type: indirect
...

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

Author: dependabot[bot]