[db2] Fix stream api example in db2 doc. (#1714)

* [db2] Fix db2 doc.

Co-authored-by: gongzhongqiang <gongzhongqiang@gigacloudtech.com>

docs/content/connectors/db2-cdc.md

@@ -50,8 +50,8 @@ Notes
 
 ###  Not support BOOLEAN type in SQL Replication on Db2
 
-Only snapshots can be taken from tables with BOOLEAN type columns. Currently SQL Replication on Db2 does not support BOOLEAN, so Debezium can not perform CDC on those tables.
-Consider using a different type.
+Only snapshots can be taken from tables with BOOLEAN type columns. Currently, SQL Replication on Db2 does not support BOOLEAN, so Debezium can not perform CDC on those tables.
+Consider using another type to replace BOOLEAN type.
 
 
 How to create a Db2 CDC table
@@ -203,36 +203,36 @@ _Note: the mechanism of `scan.startup.mode` option relying on Debezium's `snapsh
 ### DataStream Source
 
 ```java
-import org.apache.flink.api.common.eventtime.WatermarkStrategy;
 import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
-import org.apache.kafka.connect.source.SourceRecord;
+import org.apache.flink.streaming.api.functions.source.SourceFunction;
+
 import com.ververica.cdc.debezium.JsonDebeziumDeserializationSchema;
-import com.ververica.cdc.connectors.db2.Db2Source;
 
 public class Db2SourceExample {
   public static void main(String[] args) throws Exception {
-    Db2Source<SourceRecord> db2Source = Db2Source.<SourceRecord>builder()
-        .hostname("yourHostname")
-        .port(yourPort)
-        .database("yourDatabaseName") // set captured database
-        .tableList("yourSchemaName.yourTableName") // set captured table
-        .username("yourUsername")
-        .password("yourPassword")
-        .deserializer(new JsonDebeziumDeserializationSchema()) // converts SourceRecord to JSON String
-        .build();
+    SourceFunction<String> db2Source =
+            Db2Source.<String>builder()
+                    .hostname("yourHostname")
+                    .port(50000)
+                    .database("yourDatabaseName") // set captured database
+                    .tableList("yourSchemaName.yourTableName") // set captured table
+                    .username("yourUsername")
+                    .password("yourPassword")
+                    .deserializer(
+                            new JsonDebeziumDeserializationSchema()) // converts SourceRecord to
+                    // JSON String
+                    .build();
 
     StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
 
     // enable checkpoint
     env.enableCheckpointing(3000);
 
-    env
-      .fromSource(db2Source, WatermarkStrategy.noWatermarks(), "Db2 Source")
-      // set 4 parallel source tasks
-      .setParallelism(1)
-      .print().setParallelism(1); // use parallelism 1 for sink to keep message ordering
+    env.addSource(db2Source)
+            .print()
+            .setParallelism(1); // use parallelism 1 for sink to keep message ordering
 
-    env.execute("Print Db2 Snapshot + Binlog");
+    env.execute("Print Db2 Snapshot + Change Stream");
   }
 }
 ```

flink-connector-db2-cdc/src/test/java/com/ververica/cdc/connectors/db2/Db2SourceTest.java

@@ -294,7 +294,7 @@ public class Db2SourceTest extends Db2TestBase {
             assertDelete(records.get(0), "ID", 1001);
 
             // ---------------------------------------------------------------------------
-            // Step-6: trigger checkpoint-2 to make sure we can continue to to further checkpoints
+            // Step-6: trigger checkpoint-2 to make sure we can continue to further checkpoints
             // ---------------------------------------------------------------------------
             synchronized (sourceContext3.getCheckpointLock()) {
                 // checkpoint 3