update submodule

yiz · yiz · commit ca2ae9601d25 · 2020-01-15T13:32:15.000-08:00
diff --git a/stan b/stan
@@ -1 +1 @@
-Subproject commit e4c6b50f574b20f960cfde933ee8c7920ffe94c1
+Subproject commit 731b310ea7c2666ab0e9e773342593291d5ade3c
