warped_motion.c: delete unused filter_4tap[]
warped_motion.c: delete unused filter_4tap[]

Change-Id: I139808f492a9e9dcac44a36237b61231ede7edc3

luctrudeau/aom,mbebenita/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,smarter/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,mbebenita/aom,mbebenita/aom,GrokImageCompression/aom,smarter/aom,smarter/aom,mbebenita/aom,mbebenita/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,mbebenita/aom,luctrudeau/aom,smarter/aom,luctrudeau/aom,mbebenita/aom