No alert if reorg happens (#2371)

# Description
Related to staging alert:
https://cowservices.slack.com/archives/C037PB929ME/p1707099846201309

Since `EventHandler` and `OnSettlementEventUpdater` are racing to update
on each new block, in case the reorg happens and
`OnSettlementEventUpdater` is faster, it will potentially catch an event
containing tx hash that was reorged.

This PR lowers the severity of this issue (we don't want slack alerts
for this). This is a temporary fix until we make event handling
pipelined.

crates/autopilot/src/on_settlement_event_updater.rs

@@ -110,11 +110,10 @@ impl OnSettlementEventUpdater {
         let hash = H256(event.tx_hash.0);
         tracing::debug!("updating settlement details for tx {hash:?}");
 
-        let transaction = self
-            .eth
-            .transaction(hash)
-            .await?
-            .with_context(|| format!("no tx {hash:?}"))?;
+        let Some(transaction) = self.eth.transaction(hash).await? else {
+            tracing::warn!(?hash, "no tx found, reorg happened");
+            return Ok(false);
+        };
 
         let (auction_id, auction_data) =
             match Self::recover_auction_id_from_calldata(&mut ex, &transaction).await? {