[NetFlow]: Wrong timestamp

### Integration Name

NetFlow Records [netflow]

### Dataset Name

netflow.log

### Integration Version

2.23.0

### Agent Version

8.18.1

### Agent Output Type

elasticsearch

### Elasticsearch Version

8.18.1

### OS Version and Architecture

Debian GNU/Linux 12 (bookworm)

### Software/API Version

_No response_

### Error Message

I'm using `nfreplay -r file.nfcapd.202505261425 -p 2055` to send the data to elastic-agent on port 2055.

The data are ingested but the timestamp field is getting the 'net flow.exporter.timestamp' as @timestamp.
The elastic field @timestamp is:

@timestamp May 25, 2025 @ 14:25:00.000

But the event is generated 1 day after the netflow.exporter.timestamp (I don't know where is field is added.

How to fix the Netflow integration to use the netflow.flow_start_milliseconds field like the @timestamp.

### Event Original

event.created May 26, 2025 @ 14:30:41.468
event.ingested May 26, 2025 @ 14:30:51.000
netflow.exporter.timestamp May 25, 2025 @ 14:25:00.000
netflow.flow_end_milliseconds May 26, 2025 @ 14:29:59.992
netflow.flow_start_milliseconds May 26, 2025 @ 14:29:59.992

### What did you do?

The netflow integration is only the UDP host to listen on 0.0.0.0 and the UDP port to listen on 2055.

### What did you see?

@timestamp May 25, 2025 @ 14:25:00.000

### What did you expect to see?

@timestamp May 26, 2025 @ 14:29:59.992

### Anything else?

_No response_