Use newest alt image for stress node (#21180) (#21191)

## Description 

Describe the changes or additions included in this PR.

## Test plan 

How did you test the new or updated feature?

---

## Release notes

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your changes, release notes aren't required.

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that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:

Co-authored-by: Mark Logan <[email protected]>

docker/sui-antithesis/docker-compose-antithesis.yaml

@@ -146,7 +146,7 @@ services:
     networks:
       sui-network:
         ipv4_address: 10.0.0.16
-    image: stress:testing
+    image: stress:${SUI_NODE_B_TAG}
     container_name: stress
     environment:
       - RUST_LOG=info