Fix benchmark code

Author: chipshort

packages/vm/benches/main.rs

@@ -6,12 +6,12 @@ use std::thread;
 use std::time::{Duration, SystemTime};
 use tempfile::TempDir;
 
-use cosmwasm_std::{coins, Empty};
+use cosmwasm_std::{coins, Checksum, Empty};
 use cosmwasm_vm::testing::{
     mock_backend, mock_env, mock_info, mock_instance_options, MockApi, MockQuerier, MockStorage,
 };
 use cosmwasm_vm::{
-    call_execute, call_instantiate, capabilities_from_csv, Cache, CacheOptions, Checksum, Instance,
+    call_execute, call_instantiate, capabilities_from_csv, Cache, CacheOptions, Instance,
     InstanceOptions, Size,
 };