Avoid the temptation to scrape the residue off with something sharp or metal as you could scratch the windscreen. There are various things that you can use, some of which you'll hopefully already have lying around the house. Rubbing alcohol or vodka, white vinegar, nail polish remover or WD-40 can be used to soak a rag, then just leave the rag on top of the residue on the windscreen. Let it soak for a few minutes to soften the sticky residue, then wipe or scrape it off with something plastic like an old card.