Bump ember-cli-htmlbars from 2.0.3 to 4.2.0

Bumps [ember-cli-htmlbars](https://github.com/ember-cli/ember-cli-htmlbars) from 2.0.3 to 4.2.0.
- [Release notes](https://github.com/ember-cli/ember-cli-htmlbars/releases)
- [Changelog](https://github.com/ember-cli/ember-cli-htmlbars/blob/master/CHANGELOG.md)
- [Commits](ember-cli/ember-cli-htmlbars@v2.0.3...v4.2.0)

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

Author: dependabot-preview[bot]