Ousted Fox News host Tucker Carlson walked right into a prank set up by YouTubers and interviewed a fake Kate Middleton whistleblower, RadarOnline.com has learned. Carlson was duped as the interview swirled with conspiracy theories speculating the Princess of Wales’ whereabouts after she underwent abdominal surgery in January and had not been seen in public since December. British YouTubers Josh & Archie concocted the prank featuring a false Kensington Palace whistleblower that Carlson fell for. The fake whistleblower was prepared to dish all the dirty details of Kate’s photoshopped photo — an…