Update the Fluentd version to 1.19.3 due to a bug in 1.19.2: memory leak with Fluentd 1.19.2 due to cool.io

### Describe the issue
There is memory leak with fluentd version 1.19.2

See https://github.com/fluent/fluentd/issues/5285.
Could you upgrade the Fluentd version?

### To Reproduce

https://github.com/fluent/fluentd/issues/5285#issuecomment-4081028672

### Expected behavior

No memory leak

### Your Environment

```markdown
Applies to Fluentd version 1.17.2
```

### How did you install fluent operator?

_No response_

### Additional context

_No response_

Start by searching the repository for Fluentd version 1.19.2 and inspect the manifests or configuration that pin it. Review the linked upstream Fluentd issue for the affected dependency, update the relevant version reference to 1.19.3, and run the repository's applicable checks to confirm the operator still builds and the version is consistent.

Written by the indexing model from the issue text.