s/boost_factor/boost in custom_filters_score doc

I may be wrong but I think custom_filters_score used boost rather than boost factor?

docs/reference/query-dsl/queries/function-score-query.asciidoc

@@ -511,11 +511,11 @@ and the `custom_filters_score`
 "custom_filters_score": {
     "filters": [
         {
-            "boost_factor": "3",
+            "boost": "3",
             "filter": {...}
         },
         {
-            "filter": {…},
+            "filter": {...},
             "script": "_score * doc['my_numeric_field'].value / pow(param1, param2)"
         }
     ],