Bump browserslist from 4.12.0 to 4.16.6 in /assets

Bumps [browserslist](https://github.com/browserslist/browserslist) from 4.12.0 to 4.16.6.
- [Release notes](https://github.com/browserslist/browserslist/releases)
- [Changelog](https://github.com/browserslist/browserslist/blob/main/CHANGELOG.md)
- [Commits](browserslist/browserslist@4.12.0...4.16.6)

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