Update reference from DateHistogram to Histogram (#26169)
Update reference from DateHistogram to Histogram (#26169)

DateHistogram was renamed, but java api docs were not updated. This commit updates a reference to DateHistogram to the new general Histogram class.
vroyer/elassandra,vroyer/elasticassandra,vroyer/elasticassandra,strapdata/elassandra,vroyer/elasticassandra,strapdata/elassandra,vroyer/elassandra,strapdata/elassandra,vroyer/elassandra,strapdata/elassandra,strapdata/elassandra