[minor][cdc-connector][postgres] PostgresDialect removes useless code

This closes #3416.

flink-cdc-connect/flink-cdc-source-connectors/flink-cdc-base/src/main/java/org/apache/flink/cdc/connectors/base/source/assigner/StreamSplitAssigner.java

@@ -28,9 +28,6 @@ import org.apache.flink.cdc.connectors.base.source.meta.split.FinishedSnapshotSp
 import org.apache.flink.cdc.connectors.base.source.meta.split.SourceSplitBase;
 import org.apache.flink.cdc.connectors.base.source.meta.split.StreamSplit;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -42,7 +39,6 @@ import java.util.Optional;
 /** Assigner for stream split. */
 public class StreamSplitAssigner implements SplitAssigner {
 
-    private static final Logger LOG = LoggerFactory.getLogger(StreamSplitAssigner.class);
     private static final String STREAM_SPLIT_ID = "stream-split";
 
     private final SourceConfig sourceConfig;

flink-cdc-connect/flink-cdc-source-connectors/flink-connector-postgres-cdc/src/main/java/org/apache/flink/cdc/connectors/postgres/source/PostgresDialect.java

@@ -159,9 +159,7 @@ public class PostgresDialect implements JdbcDataSourceDialect {
         try (JdbcConnection jdbc = openJdbcConnection(sourceConfig)) {
             return TableDiscoveryUtils.listTables(
                     // there is always a single database provided
-                    sourceConfig.getDatabaseList().get(0),
-                    jdbc,
-                    ((PostgresSourceConfig) sourceConfig).getTableFilters());
+                    sourceConfig.getDatabaseList().get(0), jdbc, sourceConfig.getTableFilters());
         } catch (SQLException e) {
             throw new FlinkRuntimeException("Error to discover tables: " + e.getMessage(), e);
         }