Bump css-vars-ponyfill from 2.4.2 to 2.4.3

Bumps [css-vars-ponyfill](https://github.com/jhildenbiddle/css-vars-ponyfill) from 2.4.2 to 2.4.3.
- [Release notes](https://github.com/jhildenbiddle/css-vars-ponyfill/releases)
- [Changelog](https://github.com/jhildenbiddle/css-vars-ponyfill/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jhildenbiddle/css-vars-ponyfill/compare/v2.4.2...v2.4.3

)

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