Unable to provide getDatabase(): Error: AngularFireModule has not been provided at getSchedulers

### Version info

**Angular:**
12.x.x

**Firebase:**
9.x.x

**AngularFire:**
7.x.x

**Other (e.g. Ionic/Cordova, Node, browser, operating system):**
Newly generated angular project with no SSR

### How to reproduce these conditions

**Failing test unit, Stackblitz demonstrating the problem**

Clone this repo and follow the README instructions

https://github.com/thatgirlcancode/angular-fire-issue

**Steps to set up and reproduce**

1. npm install
2. Add your Firebase environment config settings in app.module
3. Run ng serve or npm run start and Navigate to http://localhost:4200/
4. You will see in browser developer tools the error: Error: AngularFireModule has not been provided at getSchedulers

**Sample data and security rules**

### Debug output

** Errors in the JavaScript console **
`Error: AngularFireModule has not been provided at getSchedulers`

** Output from `firebase.database().enableLogging(true);` **
`undefined`

** Screenshots **

### Expected behavior

Firebase Realtime Database is configured and I'm able to use injection token in Firebase Service to query the database.

I have no issues configuring Firestore in this same way. I'm able to do this same provider/injection token pattern using `initializeApp` and `getFirestore` and it works beautifully. What is the difference with `getDatabase`?

### Actual behavior

`Error: AngularFireModule has not been provided at getSchedulers` is thrown and the web page is blank.

リンクされた再現リポジトリをクローンし、その README に従ってください。まず app.module の Firebase 設定と、getDatabase を使用するサービスから始めます。その設定を、動作する Firestore のインジェクションパターンと比較し、getSchedulers エラーを追跡してください。生成されたアプリが AngularFireModule エラーなしで起動し、インジェクショントークンを通じて Firebase Realtime Database にクエリを実行できれば完了です。

索引モデルが issue の本文から書いたものです。