Bump es6-promise from 4.2.5 to 4.2.8
Bump es6-promise from 4.2.5 to 4.2.8

Bumps [es6-promise](https://github.com/stefanpenner/es6-promise) from 4.2.5 to 4.2.8.
- [Release notes](https://github.com/stefanpenner/es6-promise/releases)
- [Changelog](https://github.com/stefanpenner/es6-promise/blob/master/CHANGELOG.md)
- [Commits](https://github.com/stefanpenner/es6-promise/compare/v4.2.5...v4.2.8)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
jwalton/node-promise-breaker,jwalton/node-promise-breaker