Fix compile

Author: Caideyipi

iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/consensus/statemachine/ConfigRegionStateMachine.java

@@ -62,6 +62,7 @@
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.TimeUnit;