Save AVIF test image with speed=0
Save AVIF test image with speed=0

Reduces the size of the image by 6 kB.

jcupitt/libvips,lovell/libvips,lovell/libvips,lovell/libvips,lovell/libvips,jcupitt/libvips,jcupitt/libvips,jcupitt/libvips