[doc] remove comment about function_score faster than script sort. It is not so.
[doc] remove comment about function_score faster than script sort. It is not so.

baishuo/elasticsearch_v2.1.0-baishuo,strapdata/elassandra-test,baishuo/elasticsearch_v2.1.0-baishuo,baishuo/elasticsearch_v2.1.0-baishuo,strapdata/elassandra-test,strapdata/elassandra-test,strapdata/elassandra-test,baishuo/elasticsearch_v2.1.0-baishuo,strapdata/elassandra-test,baishuo/elasticsearch_v2.1.0-baishuo,strapdata/elassandra-test,baishuo/elasticsearch_v2.1.0-baishuo,baishuo/elasticsearch_v2.1.0-baishuo,strapdata/elassandra-test