Bump @types/ember__test-helpers from 2.8.3 to 2.9.1

Bumps [@types/ember__test-helpers](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/ember__test-helpers) from 2.8.3 to 2.9.1.
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/ember__test-helpers)

---
updated-dependencies:
- dependency-name: "@types/ember__test-helpers"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

addon/package.json

@@ -100,7 +100,7 @@
     "@types/ember__string": "^3.16.3",
     "@types/ember__template": "^4.0.5",
     "@types/ember__test": "^4.0.5",
-    "@types/ember__test-helpers": "~2.8.3",
+    "@types/ember__test-helpers": "~2.9.1",
     "@types/ember__utils": "^4.0.6",
     "@typescript-eslint/eslint-plugin": "^6.12.0",
     "@typescript-eslint/parser": "^6.13.1",