Remove validation for indices segments stats.

`OpenSearch` 2.0 uses newer version of `Lucene` (9.0) which doesn't provide segments stats info.

Ref: opensearch-project/OpenSearch#2029 opensearch-project/OpenSearch#1109
See also history for `server/src/main/java/org/opensearch/index/engine/SegmentsStats.java` in `OpenSearch` repo.

Signed-off-by: Yury Fridlyand <yuryf@bitquilltech.com>

src/OpenSearch.Client/CommonOptions/Stats/SegmentsStats.cs

@@ -30,6 +30,10 @@
 
 namespace OpenSearch.Client
 {
+	/// <summary>
+	/// OpenSearch 2.0 has Lucene upgraded up to version 9.0 which doesn't provide memory info for segments.
+	/// All fields except `count` might be zeroed.
+	/// </summary>
 	[DataContract]
 	public class SegmentsStats
 	{

tests/Tests/Cluster/ClusterStats/ClusterStatsApiTests.cs

@@ -132,12 +132,14 @@ protected void Assert(ClusterIndicesStats indices)
 
 			indices.Segments.Should().NotBeNull();
 			indices.Segments.Count.Should().BeGreaterThan(0);
-
-			indices.Segments.DocValuesMemoryInBytes.Should().BeGreaterThan(0);
-			indices.Segments.MemoryInBytes.Should().BeGreaterThan(0);
-			indices.Segments.NormsMemoryInBytes.Should().BeGreaterThan(0);
-			indices.Segments.StoredFieldsMemoryInBytes.Should().BeGreaterThan(0);
-			indices.Segments.TermsMemoryInBytes.Should().BeGreaterThan(0);
+			if (Cluster.ClusterConfiguration.Version < "2.0.0")
+			{
+				indices.Segments.DocValuesMemoryInBytes.Should().BeGreaterThan(0);
+				indices.Segments.MemoryInBytes.Should().BeGreaterThan(0);
+				indices.Segments.NormsMemoryInBytes.Should().BeGreaterThan(0);
+				indices.Segments.StoredFieldsMemoryInBytes.Should().BeGreaterThan(0);
+				indices.Segments.TermsMemoryInBytes.Should().BeGreaterThan(0);
+			}
 
 			indices.Shards.Should().NotBeNull();
 			indices.Shards.Primaries.Should().BeGreaterThan(0);