Create thumbnails from uploaded images #20907 from v3.18.0 (probably) broke uploaded gif preview

Description:

Looks like the feature Create thumbnails from uploaded images (pull request #20907 ) broke the inline preview for some (but weirdly not all) gifs.
Users were complaining about the issue so I changed "Administation > Message > Message Attachments > Enable image thumbnails to save bandwith" to disabled (it seems it was set by default to "enabled") and now the problem is gone and every gif is animated on all clients (desktop, web, mobile).

Steps to reproduce:

1. Drag and drop an animated .gif file from my desktop to a group chat in rocket.chat GUI (in a web browser for instance).
2. In the new "File Upload" window click "Send" button.

Expected behavior:

Gif animation should playback immediately.

Actual behavior:

Gif doesn't play. Instead only the first frame is displayed as a static image.
If you click on the (static) "inline" image preview the "fullscreen" preview will appear (with dimmed background) and this "fullscreen" preview will be animated.

Server Setup Information:

• Version of Rocket.Chat Server: 3.18.1
• Operating System: Debian
• Deployment Method: docker
• Number of Running Instances: 1
• DB Replicaset Oplog: ???
• NodeJS Version: v12.22.1
• MongoDB Version: 4.0.27 / mmapv1 (oplog Enabled)

Client Setup Information

• Desktop App or Browser Version: Firefox 92.0.1 (64-bit)
• Operating System: Windows 10 (21H1)

Additional context

Maybe this is also relevant?:
https://github.com/RocketChat/Rocket.Chat/pull/14086
https://github.com/RocketChat/Rocket.Chat.ReactNative/pull/2975

Start by reviewing pull request #20907 and the thumbnail setting described under Administration > Message > Message Attachments. Reproduce the issue with an animated GIF while thumbnails are enabled, then verify that the inline preview animates immediately while fullscreen preview and other listed clients remain functional.