Bumps [core-js](https://github.com/zloirock/core-js) from 2.5.3 to 2.5.6.
- [Release notes](https://github.com/zloirock/core-js/releases)
- [Changelog](https://github.com/zloirock/core-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/zloirock/core-js/compare/v2.5.3...v2.5.6)
Signed-off-by: dependabot[bot] <support@dependabot.com>