Updates the Stan submodule to 3629c5a2e.

stan-buildbot · stan-buildbot · commit b51cf0884676 · 2025-03-28T10:48:52.000-04:00
diff --git a/StanHeaders/inst/include/upstream b/StanHeaders/inst/include/upstream
@@ -1 +1 @@
-Subproject commit ff57a3027a24df69ba3bcf358ce74dad1aa4ea61
+Subproject commit 3629c5a2e814d03aae1d9e8cee23522ff7a7aa76
