Elasticsearch connector hangs for threads deadlocked

When using the connector created by org.apache.flink.streaming.connectors.elasticsearch7.ElasticsearchSink.Builder to sink data to ES(es7.7.1 and es6.8.5), flink job will finally hang for threads deadlocked after a while.

And connector created by org.apache.flink.streaming.connectors.elasticsearch6.ElasticsearchSink.Builder will not result in this deadlocked situation.

This deadlocked issue may come from this pr：https://github.com/elastic/elasticsearch/pull/41451

So upgrade version of the dependencies of ES may fix this bug.