GetFileAsync with special characters not working

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

* Unity editor version: 2020.1.8f1
* Firebase Unity SDK version: 6.16
* Source you installed the SDK: Unity Package Manager
* Problematic Firebase Component: Storage
* Other Firebase Components in use: Auth
* Additional SDKs you are using: Discord SDK, Steamworks API
* Platform you are using the Unity editor on: Windows
* Platform you are targeting: iOS, Android, and desktop
* Scripting Runtime: IL2CPP

### [REQUIRED] Please describe the issue here:

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

#### Steps to reproduce:

Have you been able to reproduce this issue with just the Firebase Unity quickstarts (this GitHub project)? **Yes.**
What's the issue repro rate? **100%**

What happened? How can we make the problem occur?
**When doing GetFileAsync() to a path that contains Cylliric characters, the file is never downloaded and the tasks gives a success result with no exceptions.**
```
storageRef.GetFileAsync("file://C:/Users/Admin/AppData/LocalLow/My Folder/Normal name/mydownloadedfile.asd"); // - Works fine
storageRef.GetFileAsync("file://C:/Users/Admin/AppData/LocalLow/My Folder/Александр/mydownloadedfile.asd"); // - Doesn't download the file
```

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