[Req] Remove black border around icon

### Your use case

#### What would you like to do?
Remove the black border around the icon.

#### Why would you like to do it?
For any phone on dark mode with a black background, the icon looks completely out of place as it appears much smaller than other icons due to the black border:

#### How would you like to achieve it?
Just remove the black border, making the icon more like the original Element app icon.

### Have you considered any alternatives?

Customizing the icon in my launcher, but that seems hacky.

### Additional context

Happy to make this change and PR if devs would accept it.

### Are you willing to provide a PR?

Yes