Incorrect Handling of Loki Plugin Configuration

[a-b-v]

Describe the bug

The Loki plugin supports using a label section as described here https://github.com/grafana/loki/blob/main/docs/sources/send-data/fluentd/_index.md#adding-labels:

<match mytag>
  @type loki
  # ...
  <label>
    container $.kubernetes.container
  </label>
  # ...
</match>

However, the reloader throws the following error when processing this configuration:

level=info msg="Configuration for namespace kfo-loki-test cannot be validated: bad label name  for <label>, must start with @"

Reproduction steps

1. Create a kfo configmap that uses the Loki plugin and includes a section as described.
2. Observe reloader Logs

Expected behavior

The reloader should correctly process the section without throwing errors.

Additional context

No response