User guide still says Stan doesn't support MAP estimate

[jgabry]

Summary:

Stan supports MAP estimation now so this part of the doc on clustering should be updated:

docs/src/stan-users-guide/clustering.Rmd

Lines 559 to 560 in cc4a208

	maximum a posteriori estimate given a double-exponential prior. Stan
	does not (yet) support maximum a posteriori estimation, so the mean and

Current Version:

v2.33.0

[jgabry]

@bob-carpenter This is in the section you wrote about correlated topic models. I could
just fix this sentence, or do you want to update this section more than that now that Stan supports MAP estimation?

[avehtari]

Pinging @bob-carpenter who asked to point out doc issues he could work on in the near future