kgo: fix one bug found by linting
We updated a timestamp variable but did not use it, now we do.
@@ -1657,7 +1657,7 @@ func (o offsetLoadMap) buildListReq(isolationLevel int8) *kmsg.ListOffsetsReques
p := kmsg.NewListOffsetsRequestTopicPartition()
p.Partition = partition
p.CurrentLeaderEpoch = offset.currentEpoch // KIP-320
- p.Timestamp = offset.at
+ p.Timestamp = timestamp
p.MaxNumOffsets = 1
parts = append(parts, p)
