update default compatible-with tests to be 9

Author: Mpdreamz

src/Elastic.Transport/Products/Elasticsearch/ElasticsearchProductRegistration.cs

@@ -50,7 +50,7 @@ public ElasticsearchProductRegistration(Type markerType) : this()
 			_metaHeaderProvider = new DefaultMetaHeaderProvider(clientVersionInfo, identifier);
 
 		// Only set this if we have a version.
-		// If we don't have a version we won't apply the vendor-based REST API compatibility Accept header.
+		// If we don't have a version, we won't apply the vendor-based REST API compatibility Accept header.
 		if (clientVersionInfo.Major > 0)
 			_clientMajorVersion = clientVersionInfo.Major;
 

tests/Elastic.Transport.IntegrationTests/Http/ApiCompatibilityHeaderTests.cs

@@ -25,13 +25,13 @@ public async Task AddsExpectedVendorInformationForRestApiCompaitbility()
 			responseMessage.RequestMessage.Content.Headers.ContentType.MediaType.Should().Be("application/vnd.elasticsearch+json");
 			var parameter = responseMessage.RequestMessage.Content.Headers.ContentType.Parameters.Single();
 			parameter.Name.Should().Be("compatible-with");
-			parameter.Value.Should().Be("8");
+			parameter.Value.Should().Be("9");
 
 			var acceptValues = responseMessage.RequestMessage.Headers.GetValues("Accept");
-			acceptValues.Single().Replace(" ", "").Should().Be("application/vnd.elasticsearch+json;compatible-with=8");
+			acceptValues.Single().Replace(" ", "").Should().Be("application/vnd.elasticsearch+json;compatible-with=9");
 
 			var contentTypeValues = responseMessage.RequestMessage.Content.Headers.GetValues("Content-Type");
-			contentTypeValues.Single().Replace(" ", "").Should().Be("application/vnd.elasticsearch+json;compatible-with=8");
+			contentTypeValues.Single().Replace(" ", "").Should().Be("application/vnd.elasticsearch+json;compatible-with=9");
 		});
 
 		var nodePool = new SingleNodePool(Server.Uri);