Katy Perry’s abrupt departure from American Idol reportedly has remaining judges Lionel Richie and Luke Bryan fearing they’re on the chopping block, RadarOnline.com has learned. Perry, 39, recently announced her exit from the singing competition — and made it sound like the move was her choice, but sources dished the Hot N Cold singer’s insensitive behavior toward contestants had fans calling for her head — and producers plotting to give her the ax! Insiders now claim Lionel, 74, and Bryan, 47, have accused longtime host Ryan Seacrest, 49, of selfishly sucking up to Idol top brass to torpedo o…