Bad spelling in Cardinality Aggregation Mapping of precision_threshold

[ictran]

According to http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-metrics-cardinality-aggregation.html, the precsion threshold should be precision_threshold, not precision_treshold

[JsonProperty("precision_treshold")]
internal int? _PrecisionTreshold { get; set; }