[Website]: Audit logs "request_body" output field

### Type of issue

Inaccurate

### What documentation page is affected

https://www.elastic.co/docs/deploy-manage/security/logging-configuration/auditing-search-queries

### What happened?

The documentation refers to a `request.body` attribute. As a end user, I would expect the final document to have the field. Instead the body is added to the field `http.request.body.content` (in Elasticsearch) which can be confusing.

Tested on ECH v9.1.2. I don't have access to the original log to know if logs is generated this way or transformed in later on.

### Additional info

_No response_

## Action
added by (@georgewallace)

This might be being returned in a place we don't expect

- Research what is the correct attribute and update the documentation