Bump css-vars-ponyfill from 1.16.2 to 1.16.3

Bumps [css-vars-ponyfill](https://github.com/jhildenbiddle/css-vars-ponyfill) from 1.16.2 to 1.16.3.
- [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/commits/v1.16.3

)

Signed-off-by: dependabot[bot] <support@dependabot.com>
Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>