[minor][hotfix] Clean unused code for schema operator&coordinator

This closes #3958

Author: Mrart

flink-cdc-runtime/src/main/java/org/apache/flink/cdc/runtime/operators/schema/regular/SchemaCoordinator.java

@@ -463,15 +463,6 @@ private boolean shouldIgnoreException(Throwable throwable) {
                 && (SchemaChangeBehavior.TRY_EVOLVE.equals(behavior));
     }
 
-    /**
-     * {@code IDLE}: Initial idling state, ready for requests. <br>
-     * {@code APPLYING}: When schema change application finishes (successfully or with exceptions)
-     */
-    private enum RequestStatus {
-        IDLE,
-        APPLYING
-    }
-
     /**
      * Before Flink CDC 3.3, we store routing rules into {@link SchemaCoordinator}'s state, which
      * turns out to be unnecessary since data stream topology might change after stateful restarts,

flink-cdc-runtime/src/main/java/org/apache/flink/cdc/runtime/operators/schema/regular/SchemaOperator.java

@@ -51,7 +51,6 @@
 
 import java.io.Serializable;
 import java.time.Duration;
-import java.time.Instant;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -242,12 +241,6 @@ RESPONSE sendRequestToCoordinator(REQUEST request) {
         }
     }
 
-    /** Visible for mocking in test cases. */
-    @VisibleForTesting
-    protected int getCurrentTimestamp() {
-        return (int) Instant.now().getEpochSecond();
-    }
-
     @VisibleForTesting
     public void registerInitialSchema(TableId tableId, Schema schema) {
         originalSchemaMap.put(tableId, schema);