Bump ember-cli-code-coverage from 1.0.0-beta.4 to 1.0.0-beta.8

Bumps [ember-cli-code-coverage](https://github.com/kategengler/ember-cli-code-coverage) from 1.0.0-beta.4 to 1.0.0-beta.8.
- [Release notes](https://github.com/kategengler/ember-cli-code-coverage/releases)
- [Changelog](https://github.com/kategengler/ember-cli-code-coverage/blob/master/CHANGELOG.md)
- [Commits](ember-cli-code-coverage/ember-cli-code-coverage@v1.0.0-beta.4...v1.0.0-beta.8)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]