Fix table_to_png image generation

[StroppaFR]

This fixes PNG image generation when using -format png. There were some extra commas in the source code.

Before

$ python main.py -in ./examples/toy -lat -format png -out .
./examples/toy 

Linear Approximation Table
Traceback (most recent call last):
  File "/tmp/SUnbox/main.py", line 150, in <module>
    print_table(table, format, filename)
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/tmp/SUnbox/sunbox/format.py", line 74, in print_table
    output = table_to_png(table)
  File "/tmp/SUnbox/sunbox/format.py", line 64, in table_to_png
    image.putpixel((x, y), color)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/site-packages/PIL/Image.py", line 2214, in putpixel
    return self.im.putpixel(xy, value)
           ~~~~~~~~~~~~~~~~^^^^^^^^^^^
TypeError: color must be int, or tuple of one, three or four elements

After

$ python main.py -in ./examples/toy -lat -format png -out . && file lat_toy.png
./examples/toy 

Linear Approximation Table

lat_toy.png: PNG image data, 16 x 16, 8-bit/color RGB, non-interlaced