Docs: Expand on `xray_trace_id` key in Logger suppresion

[heitorlessa]

What were you initially searching for in the docs?

How to suppress xray_trace_id in the Logger, as discussed in #215

Is this related to an existing part of the documentation? Please share a link: https://awslabs.github.io/aws-lambda-powertools-python/core/logger/#overriding-log-records

Describe how we could make it clearer: Explain that xray_trace_id is automatically added and updated if X-Ray is enabled in customers' Lambda function.

If you have a proposed update, please share it here

[heitorlessa]

This is now available in the docs