Bump ember-pikaday from 2.4.1 to 4.0.0

Bumps [ember-pikaday](https://github.com/adopted-ember-addons/ember-pikaday) from 2.4.1 to 4.0.0.
- [Release notes](https://github.com/adopted-ember-addons/ember-pikaday/releases)
- [Changelog](https://github.com/adopted-ember-addons/ember-pikaday/blob/master/CHANGELOG.md)
- [Commits](adopted-ember-addons/ember-pikaday@v2.4.1...v4.0.0)

---
updated-dependencies:
- dependency-name: ember-pikaday
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>