build(deps): bump @adobe/css-tools in /explorer/frontend

Bumps [@adobe/css-tools](https://github.com/adobe/css-tools) from 4.2.0 to 4.3.1.
- [Changelog](https://github.com/adobe/css-tools/blob/main/History.md)
- [Commits](https://github.com/adobe/css-tools/commits)

---
updated-dependencies:
- dependency-name: "@adobe/css-tools"
  dependency-type: indirect
...

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