[Improve] Add conditional of start.mode with timestamp in mongo cdc option rule (#6770)

Author: Hisoka-X

seatunnel-connectors-v2/connector-cdc/connector-cdc-mongodb/src/main/java/org/apache/seatunnel/connectors/seatunnel/cdc/mongodb/MongodbIncrementalSourceFactory.java

@@ -28,6 +28,8 @@
 import org.apache.seatunnel.api.table.factory.TableSourceFactoryContext;
 import org.apache.seatunnel.api.table.type.SeaTunnelDataType;
 import org.apache.seatunnel.api.table.type.SeaTunnelRow;
+import org.apache.seatunnel.connectors.cdc.base.option.SourceOptions;
+import org.apache.seatunnel.connectors.cdc.base.option.StartupMode;
 import org.apache.seatunnel.connectors.seatunnel.cdc.mongodb.config.MongodbSourceOptions;
 
 import com.google.auto.service.AutoService;
@@ -60,6 +62,10 @@ public OptionRule optionRule() {
                         MongodbSourceOptions.INCREMENTAL_SNAPSHOT_CHUNK_SIZE_MB,
                         MongodbSourceOptions.STARTUP_MODE,
                         MongodbSourceOptions.STOP_MODE)
+                .conditional(
+                        MongodbSourceOptions.STARTUP_MODE,
+                        StartupMode.TIMESTAMP,
+                        SourceOptions.STARTUP_TIMESTAMP)
                 .build();
     }