chore(deps): bump postcss-selector-parser in /website (#1965)

Bumps [postcss-selector-parser](https://github.com/postcss/postcss-selector-parser) from 6.1.4 to 6.1.6.
- [Release notes](https://github.com/postcss/postcss-selector-parser/releases)
- [Changelog](https://github.com/postcss/postcss-selector-parser/blob/6.1.6/CHANGELOG.md)
- [Commits](postcss/postcss-selector-parser@6.1.4...6.1.6)

---
updated-dependencies:
- dependency-name: postcss-selector-parser
  dependency-version: 6.1.6
  dependency-type: indirect
...

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