Remove GPDB_94_STABLE_MERGE_FIXME for CTE
Remove GPDB_94_STABLE_MERGE_FIXME for CTE

Here the check for `RTE_CTE` is correct since in GPDB, while planning, CTE is
considered similar to subquery. Hence, removing the FIXME.

Co-authored-by: Alexandra Wang <2104ed7b77de63c11d65f08ed993b286192143d2@pivotal.io>

ashwinstar/gpdb,ashwinstar/gpdb,lisakowen/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,ashwinstar/gpdb,xinzweb/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,lisakowen/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,lisakowen/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,adam8157/gpdb,jmcatamney/gpdb,xinzweb/gpdb,ashwinstar/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,lisakowen/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,jmcatamney/gpdb