[minor][pipeline-connector/doris] Fix deprecated method usage in DorisSchemaChangeManager

This closes #3959.

Author: jinkachy

flink-cdc-connect/flink-cdc-pipeline-connectors/flink-cdc-pipeline-connector-doris/src/main/java/org/apache/flink/cdc/connectors/doris/sink/DorisSchemaChangeManager.java

@@ -23,7 +23,7 @@
 
 import java.io.IOException;
 
-import static org.apache.doris.flink.catalog.doris.DorisSystem.identifier;
+import static org.apache.doris.flink.catalog.doris.DorisSchemaFactory.identifier;
 
 /** An enriched version of Doris' {@link SchemaChangeManager}. */
 public class DorisSchemaChangeManager extends SchemaChangeManager {