Update scripting.asciidoc

Fixed minor typo in the example of native scripting request.

docs/reference/modules/scripting.asciidoc

@@ -425,10 +425,12 @@ curl -XPOST localhost:9200/_search -d '{
       "functions": [
         {
           "script_score": {
+            "script": {
                 "id": "my_script",
                 "lang" : "native"
             }
           }
+        }
       ]
     }
   }