Amazon Prime Day is almost certain to set new online sales records this week, but the e-commerce giant’s annual shopping holiday doesn’t feel quite so special anymore. It’s not just that Target, Walmart and others now hold blockbuster mid-July sales of their own. These days, shoppers looking for fashion deals can open Shein’s app anytime. Now there’s also Temu, which didn’t exist when Amazon held its 2022 Prime Day, and is now the…