Unable to receive images in iOS notifications.

### [REQUIRED] Please fill in the following fields:

* Unity editor version: 2020.2.0f1
* Firebase Unity SDK version: 7.0.2
* Source you installed the SDK: UPM (.unitypackage or Unity Package Manager)
* Problematic Firebase Component: FCM (Auth, Database, etc.)
* Other Firebase Components in use: Auth,Database,Storage,RemoteConfig, FCM etc (Auth, Database, etc.)
* Additional SDKs you are using: AppsFlyer (Facebook, AdMob, etc.)
* Platform you are using the Unity editor on: Mac (Mac, Windows, or Linux)
* Platform you are targeting: iOS (iOS, Android, and/or desktop)
* Scripting Runtime: IL2CPP (Mono, and/or IL2CPP)

### [REQUIRED] Please describe the issue here:
Unable to receive image notifications (rich) via console, sent to the Unity App

(Please list the full steps to reproduce the issue. Include device logs, Unity logs, and stack traces if available.)

#### Steps to reproduce:
1. Build for iOS
2. Deploy to Xcode and build
3. Use generated token to send notifications via console
4. Send text + https image /image stored in bucket.
5. Image is ignored, only text is received
Have you been able to reproduce this issue with just the Firebase Unity quickstarts (this GitHub project)?
What's the issue repro rate? (eg 100%, 1/5 etc)
100%
What happened? How can we make the problem occur?
This could be a description, log/console output, etc.

If you have a downloadable sample project that reproduces the bug you're reporting, you will
likely receive a faster response on your issue.

#### Relevant Code:

```
// TODO(you): code here to reproduce the problem
```