[Docs] value_count supports script per 1.1

docs/reference/search/aggregations/metrics/valuecount-aggregation.asciidoc

@@ -34,6 +34,7 @@ The name of the aggregation (`grades_count` above) also serves as the key by whi
 retrieved from the returned response.
 
 ==== Script
+added[1.1]
 
 Counting the values generated by a script: