x86-64 test: remove encoding test for removed PREFETCHW[T1]
x86-64 test: remove encoding test for removed PREFETCHW[T1]

adamzhz/PeachPy,shaunstanislaus/PeachPy,lemire/PeachPy,pombredanne/PeachPy,silky/PeachPy,utensil-star/PeachPy