[DOCS] Tags Normailze For Stream processor as 9.1 (elastic#131705)

* [DOCS] Tags Normailze For Stream processor as 9.1.

* Addresses feedback.

Author: szabosteve

docs/reference/enrich-processor/index.md

@@ -84,7 +84,7 @@ Refer to [Enrich your data](docs-content://manage-data/ingest/transform-enrich/d
 [`network_direction` processor](/reference/enrich-processor/network-direction-processor.md)
 :   Calculates the network direction given a source IP address, destination IP address, and a list of internal networks.
 
-[`normalize_for_stream` processor](/reference/enrich-processor/normalize-for-stream.md)
+[`normalize_for_stream` processor](/reference/enrich-processor/normalize-for-stream.md) {applies_to}`stack: preview 9.1`
 :   Normalizes non-OpenTelemetry documents to be OpenTelemetry-compliant.
 
 [`registered_domain` processor](/reference/enrich-processor/registered-domain-processor.md)

docs/reference/enrich-processor/normalize-for-stream.md

@@ -1,5 +1,7 @@
 ---
 navigation_title: "Normalize for Stream"
+applies_to:
+  stack: preview 9.1
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/normalize-for-stream-processor.html
 ---