Changed Arrays.asList to Collections.singletonList to avoid UnsupportedOperationException

Signed-off-by: Nathalie Jonathan <[email protected]>

Author: nathaliellenaa

plugin/src/test/java/org/opensearch/ml/rest/RestMLExecuteActionTests.java

@@ -21,7 +21,7 @@
 import static org.opensearch.ml.utils.TestHelper.getMetricsCorrelationRestRequest;
 
 import java.io.IOException;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -385,7 +385,7 @@ public void testAnomalyLocalizationExecutionResponse() throws Exception {
             bucket1.setOverallAggValue(65.0);
 
             Result result = new Result();
-            result.setBuckets(Arrays.asList(bucket1));
+            result.setBuckets(Collections.singletonList(bucket1));
 
             AnomalyLocalizationOutput output = new AnomalyLocalizationOutput();
             Map<String, Result> results = new HashMap<>();