Rename 13_ball_track.py example to 13_color_track.py

[ilyatregubov]

Hello!

I think the example is better to be renamed otherwise its confusing. It doesn't really track a ball. There is nothing about a shape of an object, its just a color that matters. The actual tracking part is:

Vilib.color_detect(color="red") # close, red, green, blue, yellow , orange, purple

Cheers