[Website]: CEF field mapping mismatch

### Type of issue

Inaccurate

### What documentation page is affected

https://www.elastic.co/docs/reference/logstash/plugins/plugins-codecs-cef

### What happened?

When performing some parsing on CEF data, I found that some fields are not the same between the logstash codec plugin and the Elastic Integration.

For example for the field `deviceCustomString2`, the integration maps it to `cef.extensions.deviceCustomString2`, when the Logstash plugin maps it to `[cef][device_custom_string_2][value]` (which translate t to `cef.device_custom_string_2.value` in ES).

According to the last update of the logstash codec (2024-10-22). Its doc should be updated to match the integration mapping, which is more up to date.

Link to the Elastic integration repo: https://github.com/elastic/integrations/tree/main/packages/cef

### Additional info

_No response_