SPOILER ALERT: This story contains details about tonight's This Is Us season 2 finale “The Wedding” on NBC. Time flies when you’re watching and sobbing to This Is Us, and tonight we’ve finally reached the second season finale of the NBC/Fox series with the episode,“The Wedding”. After last season’s heart-wrenching cliffhanger where young Jack (Milo Ventimiglia) has an epic fight with Rebecca (Mandy Moore) over her singing career, familial duties, his alcoholism and his…