intro_animation nested loops using same counter

[bradanlane]

I'm not sure how this has worked in the past.

There is a loop to 50 and inside it is a loop to NATIVE_RESOLUTION. Both loops use i as their counter.

[connornishijima]

Umm, I'm not sure how this works either! Could it weirdly be because a uint16_t is used for one and a uint8_t for the other? Definitely going in the list for 4.1.0 fixes. Thanks Bradan!