Follow-up to #36663. These two pre-existing nits came up in review there and were left out of that PR to avoid review churn (comment).
Remove the "Generate a block" log line in test_reorg. It adds nothing and causes confusion. The log line above it already says "Broadcast and mine spend_3_1" and the mining only happens a few lines later in self.generate(self.nodes[0], FORK_LENGTH - 1).
Update the comment "Create a child of that transaction" in test_reorg_relay. It sits right below tx_before_reorg, so it suggests the child spends tx_before_reorg. The child actually spends tx_disconnected, so name it explicitly.
Only a log message and a comment change, so test behavior is unchanged. mempool_reorg.py passes locally.
