Bump browserslist from 4.16.3 to 4.16.6 in /tests (#389)

Bumps [browserslist](https://github.com/browserslist/browserslist) from 4.16.3 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@4.16.3...4.16.6)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]