I’m having a vision … yes, it’s time to say goodbye to Shawn and Gus, plus Lassie and Jules and the rest of the gang. (Actually, I’m not psychic, I’m reading a news release. But I think Shawn would approve.) After eight seasons, the USA Network series “Psych” will air its series finale on Wednesday at 9 p.m. (“Psych After Show” airs right after.) The show, about a super-observant goofball who pretends to be psychic so that he and his best friend Gus (the real payoff on this show) can work as consultants for the Santa Barbara police department, is admittedly an acquired taste. But those who loved, loved deeply. Plenty of teary-eyed Psych-Os around the globe will be raising a pineapple next week, as they say goodbye to some silly TV friends.