chore(deps-dev): bump ember-cli-addon-docs from 0.6.7 to 0.6.8
chore(deps-dev): bump ember-cli-addon-docs from 0.6.7 to 0.6.8

Bumps [ember-cli-addon-docs](https://github.com/ember-learn/ember-cli-addon-docs) from 0.6.7 to 0.6.8.
- [Release notes](https://github.com/ember-learn/ember-cli-addon-docs/releases)
- [Changelog](https://github.com/ember-learn/ember-cli-addon-docs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ember-learn/ember-cli-addon-docs/compare/v0.6.7...v0.6.8)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
rwjblue/ember-lifeline,rwjblue/ember-lifeline