Remove unused struct.
Remove unused struct.

It will be re-introduced in 8.4, but it's unused now.

50wu/gpdb,xinzweb/gpdb,lisakowen/gpdb,yuanzhao/gpdb,Chibin/gpdb,greenplum-db/gpdb,Chibin/gpdb,50wu/gpdb,Chibin/gpdb,cjcjameson/gpdb,Chibin/gpdb,kaknikhil/gpdb,janebeckman/gpdb,edespino/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,lisakowen/gpdb,Chibin/gpdb,ashwinstar/gpdb,edespino/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,janebeckman/gpdb,kaknikhil/gpdb,Chibin/gpdb,xinzweb/gpdb,xinzweb/gpdb,janebeckman/gpdb,adam8157/gpdb,xinzweb/gpdb,janebeckman/gpdb,Chibin/gpdb,janebeckman/gpdb,edespino/gpdb,ashwinstar/gpdb,edespino/gpdb,janebeckman/gpdb,50wu/gpdb,yuanzhao/gpdb,Chibin/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,ashwinstar/gpdb,adam8157/gpdb,jmcatamney/gpdb,50wu/gpdb,greenplum-db/gpdb,adam8157/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,50wu/gpdb,50wu/gpdb,greenplum-db/gpdb,adam8157/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,edespino/gpdb,janebeckman/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,adam8157/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,edespino/gpdb,xinzweb/gpdb,kaknikhil/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,cjcjameson/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,Chibin/gpdb,kaknikhil/gpdb,edespino/gpdb,lisakowen/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,edespino/gpdb,50wu/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,ashwinstar/gpdb,cjcjameson/gpdb,janebeckman/gpdb,jmcatamney/gpdb,lisakowen/gpdb,edespino/gpdb,kaknikhil/gpdb,Chibin/gpdb,cjcjameson/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,kaknikhil/gpdb,edespino/gpdb,janebeckman/gpdb,kaknikhil/gpdb,janebeckman/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,lisakowen/gpdb,adam8157/gpdb