Bump @ember/test-helpers from 2.2.6 to 2.2.8
Bump @ember/test-helpers from 2.2.6 to 2.2.8

Bumps [@ember/test-helpers](https://github.com/emberjs/ember-test-helpers) from 2.2.6 to 2.2.8.
- [Release notes](https://github.com/emberjs/ember-test-helpers/releases)
- [Changelog](https://github.com/emberjs/ember-test-helpers/blob/master/CHANGELOG.md)
- [Commits](https://github.com/emberjs/ember-test-helpers/compare/v2.2.6...v2.2.8)

---
updated-dependencies:
- dependency-name: "@ember/test-helpers"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
ilios/common,ilios/common