Updates the Math submodule to d959c81.

stan-buildbot · stan-buildbot · commit 59845f1ba9e6 · 2025-06-10T19:47:28.000-04:00
diff --git a/lib/stan_math b/lib/stan_math
@@ -1 +1 @@
-Subproject commit 4904f89553cd9e71f5e39075cf660910a130be21
+Subproject commit d959c81b78111e72106e6f0483ce5267546b9737
