test(opensearch): test new data_nodes_count attribute

tests/providers/aws/services/opensearch/opensearch_service_test.py

@@ -70,6 +70,7 @@ def mock_make_api_call(self, operation_name, kwarg):
                 "ClusterConfig": {
                     "DedicatedMasterEnabled": True,
                     "DedicatedMasterCount": 1,
+                    "InstanceCount": 3,
                 },
                 "CognitoOptions": {"Enabled": True},
                 "EncryptionAtRestOptions": {"Enabled": True},
@@ -178,6 +179,7 @@ class Test_OpenSearchService_Service:
         assert opensearch.opensearch_domains[0].version == "opensearch-version1"
         assert opensearch.opensearch_domains[0].dedicated_master_enabled
         assert opensearch.opensearch_domains[0].dedicated_master_count == 1
+        assert opensearch.opensearch_domains[0].data_nodes_count == 3
         assert opensearch.opensearch_domains[0].tags == [
             {"Key": "test", "Value": "test"},
         ]