Production build fails with AngularFire 7 & Firebase 9 (ES5 bundle problem)

### Version info

**Angular: 12.2.13**

**Firebase: 9.1.3**

**AngularFire: 7.2.0**

**Other (e.g. Ionic/Cordova, Node, browser, operating system): Ionic 5.8.5, Cordova 9, BraveBrowser, MacOS**

### How to reproduce these conditions

**Steps to set up and reproduce**

The problem occured when I ran `ionic build --prod`

Important! The problem appears only with Firebase 9 and AngularFire 7! With Firebase 8 and AngularFire 6 the production build works without any problem.

**Sample data and security rules**

### Debug output

```
› ionic build --prod
> ng run app:build:production
✔ Browser application bundle generation complete.
⠙ Generating ES5 bundles for differential loading...An unhandled exception occurred: {project-path}/main-es2015.059a60e139f9c6cfd626.js: Unexpected token (2461:8)

2459 | * limitations under the License.
2460 | */
> 2461 | function(de){return Promise.all(de.map(function(){var P=(0,f.Z)(function*(W){try{return{fulfilled:!0,value:yield W}}catch(Ie){return{fulfilled:!1,reason:Ie}}});return function(W){return P.apply(this,arguments)}}()))}(Io);dt.ports[0].postMessage({status:"done",eventId:Lt,eventType:Un,response:Yo})})()}_subscribe(W,Ie){0===Object.keys(this.handlersMap).length&&this.eventTarget.addEventListener("message",this.boundEventHandler),this.handlersMap[W]||(this.handlersMap[W]=new Set),this.handlersMap[W].add(Ie)}_unsubscribe(W,Ie){this.handlersMap[W]&&Ie&&this.handlersMap[W].delete(Ie),(!Ie||0===this.handlersMap[W].size)&&delete this.handlersMap[W],0===Object.keys(this.handlersMap).length&&this.eventTarget.removeEventListener("message",this.boundEventHandler)}}
| ^
2462 | /**
2463 | * @license
2464 | * Copyright 2020 Google LLC
See "/private/var/folders/hx/vt3ky4d13xvb7856_4mwlj300000gn/T/ng-FP9bZ2/angular-errors.log" for further details.
[ERROR] An error occurred while running subprocess ng.

ng run app:build:production exited with exit code 127.

Re-running this command with the --verbose flag may provide more information.

```

The exact problem is the `function(de)`. It should be `function de()`, I think..

### Expected behavior

Successful build.

### Actual behavior

Build failure

Beginne damit, den Fehler mit `ionic build --prod` zu reproduzieren, das `ng run app:build:production` aufruft. Untersuche die generierte `main-es2015.059a60e139f9c6cfd626.js` und den Angular-Schritt für Differential Loading rund um den gemeldeten Parse-Fehler; abgeschlossen ist die Aufgabe, wenn der Production-Build mit Firebase 9 und AngularFire 7 erfolgreich abgeschlossen wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.