[hotfix-#1119][pgsql] Connection cast-exception when use greenplum sink.

[FlechazoW]

Purpose of this pull request

Fix the issue of throwing connection cast-exception when use greenplum-writer.

Which issue you fix

Fixes # (1119).

Checklist:

• I have executed the 'mvn spotless:apply' command to format my code.
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• I have made corresponding changes to the documentation.
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[zlj921020]

并没有修复啊，还是包类型转换错误Caused by: java.lang.ClassCastException: com.pivotal.jdbc.greenplumbase.ddu cannot be cast to org.postgresql.core.BaseConnection，greenplum的版本：5.21.0

[zlj921020]

只要是greenplum作为目标端的都报驱动找不到，但是只有gp到gp的就可以，怀疑是源端的gp是能加载进来的，导致目标的不加载也能运行

[Paddy0523]

只要是greenplum作为目标端的都报驱动找不到，但是只有gp到gp的就可以，怀疑是源端的gp是能加载进来的，导致目标的不加载也能运行
是什么模式下运行的呢，方便贴一下脚本么