Docs reference outdated "Stack Management" navigation path — should be "Data Management"

## Summary

The ECE monitoring documentation at [ece-monitoring-ece-set-retention#available-templates](https://www.elastic.co/docs/deploy-manage/monitor/orchestrators/ece-monitoring-ece-set-retention#available-templates) references navigation paths that use "Stack Management," but the Kibana left navigation has been updated to "Data Management." Users following the docs cannot locate "Index Management" because the menu structure has changed.

## Source

This was reported via an in-product intercept survey. The user rated finding things via the left menu navigation as **"Very difficult"** and specifically called out:

> *"Trying to set up ILM as guided in [the docs]. No luck finding out where 'Index Management' is."*

## What needs to change

The documentation on the page linked above that references **"Stack Management"** as a navigation path should be updated to reflect the current Kibana nav label (**"Data Management"**).

It may also be worth auditing other docs pages that reference "Stack Management" navigation paths, as this issue could affect additional pages.

## Impact

Users following current documentation cannot complete setup tasks because the documented navigation paths no longer match the product UI.