Remove factor from DateHistogramAggregation

Closes #2124

Author: russcam

src/Nest/Aggregations/Bucket/DateHistogram/DateHistogramAggregation.cs

@@ -30,9 +30,6 @@ public interface IDateHistogramAggregation : IBucketAggregation
 		[JsonProperty("time_zone")]
 		string TimeZone { get; set; }
 
-		[JsonProperty("factor")]
-		int? Factor { get; set; }
-
 		[JsonProperty("offset")]
 		string Offset { get; set; }
 
@@ -69,7 +66,6 @@ public string Format
 
 		public int? MinimumDocumentCount { get; set; }
 		public string TimeZone { get; set; }
-		public int? Factor { get; set; }
 		public string Offset { get; set; }
 		public HistogramOrder Order { get; set; }
 		public ExtendedBounds<DateTime> ExtendedBounds { get; set; }
@@ -113,8 +109,6 @@ string IDateHistogramAggregation.Format
 
 		string IDateHistogramAggregation.TimeZone { get; set; }
 
-		int? IDateHistogramAggregation.Factor { get; set; }
-
 		string IDateHistogramAggregation.Offset { get; set; }
 
 		HistogramOrder IDateHistogramAggregation.Order { get; set; }
@@ -144,8 +138,6 @@ public DateHistogramAggregationDescriptor<T> MinimumDocumentCount(int minimumDoc
 
 		public DateHistogramAggregationDescriptor<T> TimeZone(string timeZone) => Assign(a => a.TimeZone = timeZone);
 
-		public DateHistogramAggregationDescriptor<T> Interval(int factor) => Assign(a => a.Factor = factor);
-
 		public DateHistogramAggregationDescriptor<T> Offset(string offset) => Assign(a => a.Offset = offset);
 
 		public DateHistogramAggregationDescriptor<T> Order(HistogramOrder order) => Assign(a => a.Order = order);