Bump @babel/polyfill from 7.2.5 to 7.4.4

Bumps [@babel/polyfill](https://github.com/babel/babel) from 7.2.5 to 7.4.4.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.2.5...v7.4.4

)

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