Bump clean-css from 3.4.28 to 5.3.3

Bumps [clean-css](https://github.com/clean-css/clean-css) from 3.4.28 to 5.3.3.
- [Changelog](https://github.com/clean-css/clean-css/blob/master/History.md)
- [Commits](clean-css/clean-css@v3.4.28...v5.3.3)

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

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