[Kinesis] Fix kinesis sink connector does not ack messages. (#10769)

### Motivation

Currently, when the kinesis sink connector sends the message successfully, it will not ack the message.

### Modifications

* Ack messages after the sink connector send messages successfully.

(cherry picked from commit b458b4a)

pulsar-io/kinesis/src/main/java/org/apache/pulsar/io/kinesis/KinesisSink.java

@@ -238,6 +238,7 @@ public void onSuccess(UserRecordResult result) {
                 kinesisSink.sinkContext.recordMetric(METRICS_TOTAL_SUCCESS, 1);
             }
             kinesisSink.previousPublishFailed = FALSE;
+            this.resultContext.ack();
             recycle();
         }