Fix typo in gpos step definition.
Fix typo in gpos step definition.

greenplum-db/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,greenplum-db/gpos,jmcatamney/gpdb,adam8157/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpos,adam8157/gpdb,jmcatamney/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,PengJi/gporca-comments,adam8157/gpdb,lisakowen/gpdb,lisakowen/gpdb,jmcatamney/gpdb,PengJi/gporca-comments,lisakowen/gpdb,greenplum-db/gpos,50wu/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gporca,greenplum-db/gpos,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gporca,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,adam8157/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,50wu/gpdb,PengJi/gporca-comments,xinzweb/gpdb,greenplum-db/gporca,lisakowen/gpdb,PengJi/gporca-comments,jmcatamney/gpdb,jmcatamney/gpdb,50wu/gpdb,50wu/gpdb,xinzweb/gpdb,jmcatamney/gpdb,adam8157/gpdb,greenplum-db/gporca,xinzweb/gpdb,PengJi/gporca-comments,jmcatamney/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,greenplum-db/gpdb,xinzweb/gpdb