Remove workaround for Oid collision in pg_upgrade testing
Remove workaround for Oid collision in pg_upgrade testing

Commit 98627fe797515851066bcf911e7d567876 introduced a workaround
for Oid collisions stemming partition exchange of heap relations
that lack an array type. Commit 73434db2542658cd13bd5c7e3653f2f82
introduced a preallocation check to the Oid dispatcher which now
is responsible for avoiding these collisions. Remove the workaround
from the pre-test script.

Reviewed-by: Jacob Champion <487ac4c1c30bb8aa1aeea1526e59eafc939d7768@pivotal.io>
Reviewed-by: Shaoqi Bai <21fd0b51bdb8b3d4dc3706625f40daaacd39d49b@pivotal.io>

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