Reverting unused imports and property

Author: iamjag08

ml-algorithms/src/test/java/org/opensearch/ml/engine/algorithms/agent/MLAgentExecutorTest.java

@@ -32,9 +32,7 @@
 
 import org.junit.Assert;
 import org.junit.Before;
-import org.junit.Rule;
 import org.junit.Test;
-import org.junit.rules.ExpectedException;
 import org.mockito.ArgumentCaptor;
 import org.mockito.Captor;
 import org.mockito.Mock;
@@ -142,9 +140,6 @@ public class MLAgentExecutorTest {
     @Captor
     private ArgumentCaptor<Exception> exceptionCaptor;
 
-    @Rule
-    public ExpectedException exceptionRule = ExpectedException.none();
-
     private DiscoveryNode localNode = new DiscoveryNode(
         "mockClusterManagerNodeId",
         "mockClusterManagerNodeId",