[Serverless]: Clarify the meaning of "time series" in docs

[inqueue]

Description

On https://www.elastic.co/guide/en/serverless/current/elasticsearch-manage-project.html, the wording in the Search AI Lake settings section is:

2. The volume of time series project data included in the Search Boost Window

And for search boost window:

Non-time series data is always considered search-ready. The Search Boost Window determines the volume of time series project data that will be considered search-ready.

Increasing the window results in a bigger portion of time series project data included in the total search-ready data volume.

Missing is the definition of what "time series" actually means. In serverless, it is any document in standard indices or data streams having the @timestamp field. Having the definition is important since the presence of @timestamp determines if data will be subject to the boost window. In other words, data can be time series without @timestamp via another field in which case the data will not be subject to the boost window.

Resources

The feature is already implemented in serverless.

Which documentation set does this change impact?

Elastic Cloud (Hosted and Serverless) only

Feature differences

The feature only impacts serverless.

What release is this request related to?

N/A

Collaboration model

The documentation team

Point of contact.

Main contact: @

Stakeholders:

[leemthompo]

We should highlight this in the Ingest your data section too

[kosabogi]

Related PR: #225