EVM/Tezt: make transaction replacing test not flaky

What

Make the test deterministic

Why

See https://grafana.nomadic-labs.cloud/d/tezos_flaky_tests/tezos-flaky-tests?orgId=1&from=now-7d&to=now

How

We don't even need block production, we just need an evm-node to see two transactions and observe the replacing

Manually testing the MR

tezt-etherlink alpha latest tx_pool -f evm_sequencer.ml -j 7 --loop-count 100

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR