I usually use rubbing alcohol to remove stuff like that. Can be a little tricky since it’ll likely leave a cloudy residue depending on how much there it. I’m sure there are maybe more successful ways, though. But, honestly, I’d keep any picture discs out of those PVC sleeves if you can, because they can cause misting on the record (though I assume since it’s been so long, this has likely happened already). I have the Born This Way box set, and noticed it happening, and immediately put the discs in safer inner sleeves to keep inside the PVC ones.