Updates the Stan submodule to 22c3716.

stan-buildbot · stan-buildbot · commit d0d32a76954a · 2020-12-30T21:02:23.000-05:00
diff --git a/stan b/stan
@@ -1 +1 @@
-Subproject commit 038ef009af913dd9ce0ff155f0d6d4217a8fe045
+Subproject commit 22c371660355ace9188255530af8c7e9baf5e840
