SUG on multi-logit regression is out-of-date

[jsocolar]

SUG on multi-logit regression https://mc-stan.org/docs/2_29/stan-users-guide/multi-logit.html

suggests that the user has to loop row-wise since there's not a vectorized categorical logit. This is out-of-date.

See https://mc-stan.org/docs/2_29/functions-reference/categorical-distribution.html and https://mc-stan.org/docs/2_29/functions-reference/categorical-logit-glm.html