[ES|QL][Docs] Current Docs State counter field is unsupported, but it is technically supported via casting

[BenB196]

Elasticsearch Version

8.15.x+

Installed Plugins

No response

Java Version

bundled

OS Version

Container

Problem Description

In the ES|QL Docs for Unsupported types it mentions that the TSDS counter field is currently unsupported, however, this isn't technically true; #107877 added "support" for this type via explicit casting. It would be helpful to have the documentation indicate that there is a way to leverage "partially" supported fields.

Steps to Reproduce

N/A

Logs (if relevant)

No response

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[emilywcai]

@BenB196 i've created a PR with the updated documentation. Please let me know if it looks good!