Bump ember-power-calendar from 1.5.2 to 1.8.0

Bumps [ember-power-calendar](https://github.com/cibernox/ember-power-calendar) from 1.5.2 to 1.8.0.
- [Release notes](https://github.com/cibernox/ember-power-calendar/releases)
- [Changelog](https://github.com/ember-power-addons/ember-power-calendar/blob/master/CHANGELOG.md)
- [Commits](ember-power-addons/ember-power-calendar@v1.5.2...v1.8.0)

---
updated-dependencies:
- dependency-name: ember-power-calendar
  dependency-version: 1.8.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]