Worst. Shower. Ever. At least, that's what's being teased in the latest poster for The Grudge reboot starring Andrea Riseborough, Betty Gilpin, Demián Bechir, and Lin Shaye. The latest poster for the forthcoming reboot arrives on the 15th anniversary of the release of the 2004 English-language remake of the modern Japanese horror classic which starred Sarah Michelle Gellar. Fans of Gellar's The Grudge will recognize an infamous moment recreated specially for this new poster. That moment? When Karen (Gellar) feels a hand gripping the back of her head while she showers. It looks like director/…