Bump rsvp from 4.8.3 to 4.8.4
Bump rsvp from 4.8.3 to 4.8.4

Bumps [rsvp](https://github.com/tildeio/rsvp.js) from 4.8.3 to 4.8.4.
- [Release notes](https://github.com/tildeio/rsvp.js/releases)
- [Changelog](https://github.com/tildeio/rsvp.js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/tildeio/rsvp.js/compare/v4.8.3...v4.8.4)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
kpfefferle/ember-cli-deploy-cloudfront