Updates the Stan submodule to 4786757ad.

stan-buildbot · stan-buildbot · commit ee72fc31b577 · 2026-03-11T22:52:01.000-04:00
diff --git a/StanHeaders/inst/include/upstream b/StanHeaders/inst/include/upstream
@@ -1 +1 @@
-Subproject commit 396c27a1cae07518afb981e4cd40f22989ec0dc8
+Subproject commit 4786757adb2d09cf8c2a834da001bc1a515f3c96
