Fix typo in "handing" (missing "l") (#71383)

docs/reference/ingest.asciidoc

@@ -576,7 +576,7 @@ PUT _ingest/pipeline/my-pipeline
 
 [discrete]
 [[handling-pipeline-failures]]
-=== Handing pipeline failures
+=== Handling pipeline failures
 
 A pipeline's processors run sequentially. By default, pipeline processing stops
 when one of these processors fails or encounters an error.