stickers: Many of the videoplasty gifs have a white edge around them on the dark theme

I am not sure how solvable this is, but it makes them look a little rough. Some are much worse than others (depending on image contents) two reasonably bad ones are:


Start by reproducing the two examples from the linked screenshots with the stickers on the dark theme, then trace where the videoplasty GIF assets are rendered or prepared. Done means the affected GIFs no longer show a white edge on the dark theme and the result is visually checked against the reported examples.

Written by the indexing model from the issue text.