Added missing type hint in FunctionScoreQuery.
Added missing type hint in FunctionScoreQuery.

Closes #74.

mansimas/ElasticsearchDSL,saimaz/ElasticsearchDSL,asev/ElasticsearchDSL,abhiesa-tolexo/ElasticsearchDSL,tadcka/ElasticsearchDSL,ongr-io/ElasticsearchDSL