Add comment explaining test case

tests/expected/dead-invalid-access-via-raw/main.rs

@@ -1,12 +1,17 @@
 // Copyright Kani Contributors
 // SPDX-License-Identifier: Apache-2.0 OR MIT
+//
+// This test checks an issue reported in github.com/model-checking/kani#3063.
+// The access of the raw pointer should fail because the value being dereferenced has gone out of
+// scope at the time of access.
 
 #[kani::proof]
 pub fn check_invalid_ptr() {
  let raw_ptr = {
  let var = 10;
  &var as *const _
  };
+
  // This should fail since it is de-referencing a dead object.
  assert_eq!(unsafe { *raw_ptr }, 10);
 }