[In one Weekend] cam::get_ray input parameters sudden change

[mratsim]

Looking into the camera implementation, the initial parameters where u, v and they changed to s, t without highlighting.

I assume they were supposed to be u, v to keep in line with the figures and s, t was a leftover from a previous change.

[hollasch]

Thank you. Yes, I actually noticed (and have a correction for this) yesterday, when I went through the entire book. Lots of little mistakes to be fixed in book 1, including this one.

Keeping this one open, as I haven't created separate issues for the problems I've encountered.

[hollasch]

Resolved in PR #625