Fixed split processor example

docs/reference/ingest/ingest-node.asciidoc

@@ -1208,7 +1208,7 @@ Splits a field into an array using a separator character. Only works on string f
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 {
   "split": {
-    "field": ",",
+    "field": "my_field",
     "separator": "\\s+" <1>
   }
 }