Remove masks div 255 in save_images

[nbswords]

Hi there, I found that the output masks are divided by 255, this will cause all output masks to scale to 0~1 and make the masks in Google Drive / RealOcc-Wild and RealOcc black images.

I am just wondering if this is what you expected. This could be misinterpreted as corrupted images. Because all other datasets with masks (11k-Hands, CelebAMask-HQ...) store their mask images in 0~255 format.