fix: log field name

Author: guanzo

src/index.js

@@ -67,7 +67,7 @@ class Saturn {
       log.httpStatusCode = res.status
       log.cacheHit = headers.get('saturn-cache-status') === 'HIT'
       log.nodeId = headers.get('saturn-node-id')
-      log.transferId = headers.get('saturn-transfer-id')
+      log.requestId = headers.get('saturn-transfer-id')
       log.httpProtocol = headers.get('quic-status')
 
       if (!res.ok) {