[Easy] Update contracts to v0.4.3 (#1423)

This allows us to run with the xDAI deployment (part of #1418).

### Test Plan
```
cargo run --bin driver -- --node-url https://xdai.poanetwork.dev  --rpc-timeout 60000 --orderbook-file target/orderbook_xdai.bin --network-id 100 --private-key <your PK> --solver-type opensolver --native-token-id 0
```

Place overlapping orders on xDAI using contract scripts and see successful solution submitted (e.g. https://blockscout.com/poa/xdai/tx/0x8cf98c64ebc08632f846cbb1c3d63e110dd6b6f093b6ec6e3f103c6b09d6c196/token-transfers)