[Docs] Update ingest.asciidoc (#26599)

Added a brief note to clarify where configured pipelines are stored (cluster state).

docs/reference/ingest.asciidoc

@@ -18,7 +18,8 @@ node.ingest: false
 To pre-process documents before indexing, you <<pipeline,define a pipeline>> that specifies
 a series of <<ingest-processors,processors>>. Each processor transforms the document in some way.
 For example, you may have a pipeline that consists of one processor that removes a field from
-the document followed by another processor that renames a field.
+the document followed by another processor that renames a field. Configured pipelines are then stored
+in the <<cluster-state,cluster state>>.
 
 To use a pipeline, you simply specify the `pipeline` parameter on an index or bulk request to
 tell the ingest node which pipeline to use. For example: