Update dependency @ember/test-waiters to v4

Author: renovate[bot]

package.json

@@ -61,7 +61,7 @@
     "@ember/render-modifiers": "2.1.0",
     "@ember/string": "3.1.1",
     "@ember/test-helpers": "4.0.4",
-    "@ember/test-waiters": "3.1.0",
+    "@ember/test-waiters": "4.0.0",
     "@embroider/compat": "3.7.0",
     "@embroider/core": "3.4.19",
     "@embroider/webpack": "4.0.8",