Bump ember-source from 3.23.0 to 3.28.1 in /smoke-test-app (#764)

Bumps [ember-source](https://github.com/emberjs/ember.js) from 3.23.0 to 3.28.1.
- [Release notes](https://github.com/emberjs/ember.js/releases)
- [Changelog](https://github.com/emberjs/ember.js/blob/master/CHANGELOG.md)
- [Commits](emberjs/ember.js@v3.23.0...v3.28.1)

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

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

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

smoke-test-app/package.json

@@ -39,7 +39,7 @@
     "ember-maybe-import-regenerator": "^0.1.6",
     "ember-qunit": "^4.6.0",
     "ember-resolver": "^8.0.3",
-    "ember-source": "~3.23.0",
+    "ember-source": "~3.28.1",
     "eslint-plugin-ember": "^8.14.0",
     "loader.js": "^4.7.0",
     "qunit-dom": "^1.6.0"