apng sticker is not animated

### Steps to reproduce

* Send an animated apng sticker.
* watch at the send sticker

example event:
```json
{
"content": {
"body": "elephant.png",
"info": {
"h": 200,
"mimetype": "image/apng",
"size": 379013,
"w": 240
},
"url": "mxc://lukas1818.de/OqhTVIyZjrIPNovpWnwJShym"
},
"type": "m.sticker",
"room_id": RESTRAINED

}
```

### Outcome

#### What did you expect?
An animated sticker. Like on element desktop and fluffy chat android.
#### What happened instead?
A static image/sticker is show instead.

### Your phone model

XQ-BT52

### Operating system version

13

### Application version and app store

1.6.12 F-Droid

### Homeserver

https://github.com/msrd0/docker-synapse

### Will you send logs?

No

### Are you willing to provide a PR?

No