Disable flaky stack-or-heap test

Author: liam923

tests/test-dirs/dune

@@ -29,3 +29,10 @@
   (applies_to
      ; Enable this test when the Stdlib.Effect module is added.
      issue1558))
+
+; TODO: this test is flaky. See
+; https://github.com/janestreet/merlin-jst/actions/runs/12831007336/job/35788214467?pr=124
+(cram
+  (enabled_if false)
+  (applies_to
+    stack-or-heap))