fix PostgreSQL minimum timestamp precision

Author: kgeis

flink-connector-jdbc-postgres/src/main/java/org/apache/flink/connector/jdbc/postgres/database/dialect/PostgresDialect.java

@@ -38,7 +38,7 @@ public class PostgresDialect extends AbstractDialect {
     // Define MAX/MIN precision of TIMESTAMP type according to PostgreSQL docs:
     // https://www.postgresql.org/docs/12/datatype-datetime.html
     private static final int MAX_TIMESTAMP_PRECISION = 6;
-    private static final int MIN_TIMESTAMP_PRECISION = 1;
+    private static final int MIN_TIMESTAMP_PRECISION = 0;
 
     // Define MAX/MIN precision of DECIMAL type according to PostgreSQL docs:
     // https://www.postgresql.org/docs/12/datatype-numeric.html#DATATYPE-NUMERIC-DECIMAL