Bump @babel/preset-env from 7.7.4 to 7.7.6

Bumps [@babel/preset-env](https://github.com/babel/babel) from 7.7.4 to 7.7.6.
- [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/v7.7.4...v7.7.6)
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