Reduce object-bits for test to avoid OOM

tests/expected/function-contract/history/stub.rs

@@ -1,6 +1,6 @@
 // Copyright Kani Contributors
 // SPDX-License-Identifier: Apache-2.0 OR MIT
-// kani-flags: -Zfunction-contracts
+// kani-flags: -Zfunction-contracts --enable-unstable --cbmc-args --object-bits 8
 
 #[kani::ensures(|result| old(*ptr + *ptr) == *ptr)]
 #[kani::requires(*ptr < 100)]