[EASY] Fix outdated comment (#113)

This PR edits a comment that was outdated and led to some confusion
about whether the code can properly handle multiple txs from the same
environment in the same block (the answer is that it indeed handles them
properly).

Identical PR in the solver rewards repo
[here](cowprotocol/solver-rewards#402).

src/sql/orderbook/barn_batch_rewards.sql

@@ -87,7 +87,7 @@ order_surplus AS (
         JOIN settlement_scores ss -- contains block_deadline
         ON s.auction_id = ss.auction_id
         JOIN trades t -- contains traded amounts
-        ON s.block_number = t.block_number -- log_index cannot be checked, does not work correctly with multiple auctions on the same block
+        ON s.block_number = t.block_number -- given the join that follows with the order execution table, this works even when multiple txs appear in the same block
         JOIN order_data od -- contains tokens and limit amounts
         ON t.order_uid = od.uid
         JOIN order_execution oe -- contains surplus fee

src/sql/orderbook/prod_batch_rewards.sql

@@ -87,7 +87,7 @@ order_surplus AS (
         JOIN settlement_scores ss -- contains block_deadline
         ON s.auction_id = ss.auction_id
         JOIN trades t -- contains traded amounts
-        ON s.block_number = t.block_number -- log_index cannot be checked, does not work correctly with multiple auctions on the same block
+        ON s.block_number = t.block_number -- given the join that follows with the order execution table, this works even when multiple txs appear in the same block
         JOIN order_data od -- contains tokens and limit amounts
         ON t.order_uid = od.uid
         JOIN order_execution oe -- contains surplus fee