Bump @babel/core from 7.6.3 to 7.6.4

Bumps [@babel/core](https://github.com/babel/babel) from 7.6.3 to 7.6.4.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](babel/babel@v7.6.3...v7.6.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>