Update dependency @ember/test-helpers to v4 (rust-lang#9302)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -59,7 +59,7 @@
     "@ember/optional-features": "2.1.0",
     "@ember/render-modifiers": "2.1.0",
     "@ember/string": "3.1.1",
-    "@ember/test-helpers": "3.3.1",
+    "@ember/test-helpers": "4.0.2",
     "@ember/test-waiters": "3.1.0",
     "@embroider/compat": "3.6.0",
     "@embroider/core": "3.4.14",