Make @ember/test-helpers a dependency (#521)

Author: RobbieTheWagner

README.md

@@ -204,7 +204,7 @@ this using `mockCognitoUser`:
 
 ```js
 import { authenticateSession } from "ember-simple-auth/test-support";
-import { mockCognitoUser } from "ember-cognito/test-support";
+import { mockCognitoUser } from "ember-cognito/test-support/index";
 
 module("Acceptance | authenticated route", function (hooks) {
   test("authenticated route", async function (assert) {

package.json

@@ -47,6 +47,7 @@
   "dependencies": {
     "@aws-amplify/auth": "^6.16.0",
     "@aws-amplify/core": "^6.13.3",
+    "@ember/test-helpers": "^5.4.0",
     "@embroider/addon-shim": "^1.10.0",
     "amazon-cognito-identity-js": "^6.3.15",
     "decorator-transforms": "^2.3.0",
@@ -59,7 +60,6 @@
     "@babel/runtime": "^7.28.4",
     "@ember/app-tsconfig": "^1.0.3",
     "@ember/library-tsconfig": "^1.1.3",
-    "@ember/test-helpers": "^5.4.0",
     "@ember/test-waiters": "^4.1.1",
     "@embroider/addon-dev": "^8.1.0",
     "@embroider/compat": "^4.1.8",