[DOCS] Clarify document updates don't apply ingest pipelines (#82232) (#82328)

Adding text to clarify that the default pipeline only applies to indexing requests, not updates.

Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>
(cherry picked from commit 4e6e4eab2297e949ec994e688dad46290d018022)

Co-authored-by: Mike Barretta <mike.barretta@elastic.co>

docs/reference/ingest.asciidoc

@@ -262,8 +262,8 @@ POST _reindex
 === Set a default pipeline
 
 Use the <<index-default-pipeline,`index.default_pipeline`>> index setting to set
-a default pipeline. {es} applies this pipeline if no `pipeline` parameter
-is specified.
+a default pipeline. {es} applies this pipeline to indexing requests if no
+`pipeline` parameter is specified.
 
 [discrete]
 [[set-final-pipeline]]