Rename fielddata_fields to docvalue_fields (#8317)

The parameter fielddata_fields is deprecated and removed in 5.0 https://github.com/elastic/elasticsearch/issues/19027

public/app/plugins/datasource/elasticsearch/query_builder.js

@@ -119,7 +119,7 @@ function (queryDef) {
     }
 
     query.script_fields = {},
-    query.fielddata_fields = [this.timeField];
+    query.docvalue_fields = [this.timeField];
     return query;
   };