[Website]: ML Aggregating data for faster performance missing information on how to use filters with single bucket aggregations with the detector

### Type of issue

Missing information

### What documentation page is affected

https://www.elastic.co/docs/explore-analyze/machine-learning/anomaly-detection/ml-configuring-aggregation

### What happened?

Add an explanation that describes that the name of the bucket of the single bucket aggregation you want to use will need to be unique for the entire aggregation and is referenced in the detector just by the name of the bucket, not a path to it with the filter name.

### Additional info

_No response_