Bump @ember/test-helpers from 2.9.4 to 2.9.6 in /smoke-test-app

Bumps [@ember/test-helpers](https://github.com/emberjs/ember-test-helpers) from 2.9.4 to 2.9.6.
- [Release notes](https://github.com/emberjs/ember-test-helpers/releases)
- [Changelog](https://github.com/emberjs/ember-test-helpers/blob/v2.9.6/CHANGELOG.md)
- [Commits](emberjs/ember-test-helpers@v2.9.4...v2.9.6)

---
updated-dependencies:
- dependency-name: "@ember/test-helpers"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

smoke-test-app/package-lock.json

@@ -33,7 +33,7 @@
   "devDependencies": {
     "@ember/optional-features": "^2.0.0",
     "@ember/string": "^3.0.1",
-    "@ember/test-helpers": "~2.9.3",
+    "@ember/test-helpers": "~2.9.6",
     "@embroider/test-setup": "^3.0.0",
     "@glimmer/component": "^1.1.2",
     "@glimmer/tracking": "^1.1.2",