Backport PR #5083 on branch yt-4.4.x (BUG: fix compatibility with matplotlib 3.10 for images that have both a custom background color and a non-transparent 'bad' color)

Backport PR #5083 on branch yt-4.4.x (BUG: fix compatibility with matplotlib 3.10 for images that have both a custom background color and a non-transparent 'bad' color) #8509