def crop_image(img, rect): Remove one pixel

When using crop_image, the returned image is one pixel smaller.

This is the line in aircv.py

```
x_max, y_max = min(width - 1, x_max), min(height - 1, y_max)
img_crop = img[y_min:y_max, x_min:x_max]

```

I don't understant why we remove one pixel
Sorry for my english