"verfetch: APM Server information endpoint returned no body" in lambda invocations

While looking at a separate Lambda issue, this debug log output was noticed:

```json
{
"log.level": "debug",
"@timestamp": "2022-11-18T12:26:27.708Z",
"log": {
"logger": "elastic-apm-node"
},
"event.module": "apmclient",
"ecs": {
"version": "1.6.0"
},
"message": "verfetch: APM Server information endpoint returned no body, often this indicates authentication (\"apiKey\" or \"secretToken\") is incorrect"
}
```

In this case it shouldn't have been due to auth issues, because reporting of trace data was working fine.

I noticed this when only looking at logs for a single invocation, so I don't know if this happens all the time or if that one was a fluke. It is worth a look. Currently APM server sniffing isn't *needed* for lambda instrumentation, but it might be in the future.