highbd_quantize_neon.c: remove unneeded assert.h
highbd_quantize_neon.c: remove unneeded assert.h

Change-Id: I041f5fb23b856a2b519669b5bf8a40d3772b4a6e

webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx