Add support for @ember/test-waiters v4

This release is API compatible, so we can widen the range.

Author: Windvis

packages/ember-simple-auth/package.json

@@ -29,7 +29,7 @@
     "release": "npm publish"
   },
   "dependencies": {
-    "@ember/test-waiters": "^3",
+    "@ember/test-waiters": "^3 || ^4",
     "@embroider/addon-shim": "^1.0.0",
     "@embroider/macros": "^1.0.0",
     "ember-cookies": "^1.3.0"