Firebase files appears on Files.app

### [REQUIRED] Step 2: Describe your environment

* Xcode version: latest
* Firebase SDK version: latest
* Firebase Component: Database
* Component version: latest

### [REQUIRED] Step 3: Describe the problem

When I opting the app to be appeared in the Files app, there is a Firebase folder that contains “server_data” and “writes” folders and inside each of them there are multiple files, I think the Firebase folder should be hidden, right?

#### Steps to reproduce:

Opt in with Files app: Add these keys to your Info.plist and set their values to YES: "Application supports iTunes file sharing" and "Supports opening documents in place", then run the app.