They grow up so fast! Kendall Jenner and Kylie Jenner have a big reason to be celebrating these days—they graduated high school! Although they're in different classes, both girls decided to celebrate with one big party Thursday hosted by none other than Ryan Seacrest. The multi-hyphenate posted a selfie with the two grads on Instagram, writing, "Just had the honor of hosting @kendalljenner @kyliejenner's graudation. Congrats proud of u." Kylie is donning the classic graduation cap while Kendall opted for a hat-free look. It must have been an extravagant affair because it seems almost everyone was in attendance, including Kylie's rumored boyfriend Tyga. Khloé Kardashian,...