Remove a GPDB_90_MERGE_FIXME
Remove a GPDB_90_MERGE_FIXME

This asserssion has been commented out for 6 months and ORCA works just fine
without it.

Authored-by: Alexandra Wang <1ff6f5a716ee0f31a78d8f11fd50880e51e3d194@gmail.com>

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