Bump ember-cli-htmlbars from 5.3.1 to 5.7.1 in /smoke-test-app (#759)

Bumps [ember-cli-htmlbars](https://github.com/ember-cli/ember-cli-htmlbars) from 5.3.1 to 5.7.1.
- [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@v5.3.1...v5.7.1)

---
updated-dependencies:
- dependency-name: ember-cli-htmlbars
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]