[Website]: Fix missing OTLP auth header and incorrect dataset attribute in Claude Code integration doc

### Before you submit

- [x] This issue is about a documentation page, flow, or piece of content.

### Type of issue

Inaccurate

### What documentation page or section is affected

https://www.elastic.co/docs/reference/integrations/claude_code

### What happened?

In the [Claude Code integration documentation](https://www.elastic.co/docs/reference/integrations/claude_code#option-a-managed-otlp-motlp-recommended), the environment variable snippets under Option A and Option B contain two issues:

1. **Missing Authorization Header:** Both options are missing the authorization header snippet:
```bash
export OTEL_EXPORTER_OTLP_HEADERS="Authorization=ApiKey "

2. Incorrect Resource Attribute Dataset: The data_stream.dataset value is currently incorrect:

* Current:
```export OTEL_RESOURCE_ATTRIBUTES="data_stream.dataset=claude_code.events.otel"```

* Expected:
```export OTEL_RESOURCE_ATTRIBUTES="data_stream.dataset=claude_code"```

### Additional info

_No response_

Open the Claude Code integration documentation page and review the environment-variable snippets under Option A and Option B. Add the missing OTLP authorization header and correct the data_stream.dataset value in both sections, then verify that both options show the expected snippets.

Written by the indexing model from the issue text.