[aws_rds_otel]: Network receive/transmit panels show KB instead of KB/s

## Integration Name
AWS RDS Metrics OpenTelemetry Assets [`packages/aws_rds_otel`]

## Dataset Name
`aws.rds.otel`

## Integration Version
`0.11.1` (current on `main`)

## Agent Version
N/A — content package (Kibana dashboard assets only)

## Agent Output Type
elasticsearch

## Elasticsearch Version
N/A — content package

## OS Version and Architecture
N/A — content package

## Software/API Version
Amazon CloudWatch RDS metrics: `NetworkReceiveThroughput`, `NetworkTransmitThroughput`

## Error Message
N/A

## Event Original
N/A

## What did you do?
Opened the AWS RDS Metrics OpenTelemetry instance drilldown dashboard and inspected the Network receive / Network transmit metric cards and time-series panels.

Dashboard: [`aws_rds_otel-36df60a8-6a6e-4f72-96ce-a3533d24901a.json`](https://github.com/elastic/integrations/blob/main/packages/aws_rds_otel/kibana/dashboard/aws_rds_otel-36df60a8-6a6e-4f72-96ce-a3533d24901a.json)

Affected panels:
- `nico-rdsid-card-netrx` / `nico-rdsid-chart-netrx` — Network receive (`NetworkReceiveThroughput`)
- `nico-rdsid-card-nettx` / `nico-rdsid-chart-nettx` — Network transmit (`NetworkTransmitThroughput`)

## What did you see?
Those panels format values with the Kibana `bytes` formatter (`"format": {"id": "bytes", "params": {"decimals": 1}}`), so the UI shows a static size unit such as **KB** (or MB, etc.).

## What did you expect to see?
A **rate** unit such as **KB/s** (bytes per second).

These CloudWatch metrics are throughput (bytes/second), not a cumulative byte count. AWS documents `NetworkTransmitThroughput` as outgoing network traffic in bytes per second ([AWS docs](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/rds-metrics.html#rds-cw-metrics-instance); same for receive).

## Anything else?
Likely fix: change the Lens column format on the four panels from `bytes` to a bytes-per-second formatter (e.g. `bytesPerSecond`, if that is the ID used elsewhere in Kibana Lens field formats), so the displayed unit is `KB/s` / `MB/s` rather than `KB` / `MB`.

No ingest/pipeline change expected — this is a dashboard formatting bug only.