Any evocation of fireFunctions.httpsCallable make Angular Zone instable

### Version info

**Angular:**
12.1.1

**Firebase:**
9.1.3

**AngularFire:**
7.1.0

**Other (e.g. Ionic/Cordova, Node, browser, operating system):**
rxjs: 7.2.0

### How to reproduce these conditions

Any evocation of `fireFunctions.httpsCallable` make Angular Zone instable.

**Context**

In my angular application, I have a code that detects pending tasks executed inside Angular Zone. I noticed after upgrade on 7.1.0 that evocation of httpCallables leave long living tasks in the Zone. This was never an issue before. Even wrapping those calls into `ngZone.runOutsideAngular` doesn't help. Example:

```typescript
import {AngularFireFunctions} from '@angular/fire/compat/functions';
//...
constructor(private readonly fireFunctions: AngularFireFunctions) {
}

this.fireFunctions.httpsCallable('myFunc')(data); // this code creates a long living task inside zone and make it unstable

```

### Expected behavior

Evocation of httpCallable functions must not make zone unstable.

Reproduisez le problème avec Angular 12.1.1, Firebase 9.1.3, AngularFire 7.1.0 et RxJS 7.2.0 en utilisant AngularFireFunctions depuis @angular/fire/compat/functions. Commencez par httpsCallable et vérifiez comment son invocation interagit avec Angular Zone, notamment lorsqu’elle est enveloppée dans ngZone.runOutsideAngular. Le travail est terminé lorsque les invocations de callables ne laissent plus de tâches en attente à long terme et ne rendent plus Zone instable.

Rédigé par le modèle d'indexation à partir du texte de l'issue.