Storage: uploadBytes() does not use proper ContentType

### Version info

**Angular:** 13.3.0

**Firebase:** 10.5.0

**AngularFire:** 7.2.1

### How to reproduce these conditions

**Steps to set up and reproduce**

```
import { ref, Storage, uploadBytes } from '@angular/fire/storage';

@Component({
template: ``
})
export class UploadComponent {

constructor(private storage: Storage) {}

async upload(fileInput: any) {
const file: File = fileInput.files[0];
await uploadBytes(ref(this.storage, '/images'), file, { contentType: 'image/png' });
// -> content-type of the POST request is multipart/related instead of image/png and thus firestore security rules fail with 403!
}
}
```

**Sample data and security rules**

```
rules_version = '2';
service firebase.storage {
match /b/{bucket}/o {
match /{allPaths=**} {
allow read, write: if false;
}
match /images/{allPaths=**} {
allow read: true;
allow write: if resource.contentType == 'image/png';
}
}
```

### Debug output

** Errors in the JavaScript console **
```
Firebase Storage: User does not have permission to access 'images/demo.png'. (storage/unauthorized)
```

** Screenshots **

### Expected behavior

File is sucessfully uploaded, with contentType = 'image/png'

### Actual behavior

With enabled security rule, file file fails to upload (when checking network request, the contentType is set to 'multipart/related'. As soon as security rule is disabled (ie allow write: if true;) everything works perfectly.

Beginne beim Einstiegspunkt uploadBytes() und reproduziere das Problem mit dem Beispiel für Angular 13.3.0, Firebase 10.5.0 und AngularFire 7.2.1. Untersuche die generierte Upload-Anfrage und die Verarbeitung der Firebase-Storage-Metadaten; abgeschlossen ist die Aufgabe, wenn die Anfrage contentType: 'image/png' berücksichtigt und die bereitgestellte Sicherheitsregel den Upload erlaubt.

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