Document LLM data API timestamp limit (#30657)

* Update timestamp limit

We check if the timestamp on the submitted LLM traces and spans is within the last 24 hours for the API to ingest them.

* Update content/en/llm_observability/instrumentation/api.md

Co-authored-by: Alex Barksdale <[email protected]>

* Update content/en/llm_observability/instrumentation/api.md

Co-authored-by: Bryce Eadie <[email protected]>

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Co-authored-by: Alex Barksdale <[email protected]>
Co-authored-by: Bryce Eadie <[email protected]>

Author: 3 people

content/en/llm_observability/instrumentation/api.md

@@ -10,6 +10,8 @@ aliases:
 
 The LLM Observability API provides an interface for developers to send LLM-related traces and spans to Datadog. If your application is written in Python or Node.js, you can use the [LLM Observability SDKs][1].
 
+The API accepts spans with timestamps no more than 24 hours old, allowing limited backfill of delayed data.
+
 ## Spans API
 
 Use this endpoint to send spans to Datadog. For details on the available kinds of spans, see [Span Kinds][2].