Remove no-longer-used PageManagerMode enum.
Remove no-longer-used PageManagerMode enum.

pavanvd/postgres-xl,techdragon/Postgres-XL,tpostgres-projects/tPostgres,greenplum-db/gpdb,xinzweb/gpdb,Quikling/gpdb,CraigHarris/gpdb,janebeckman/gpdb,postmind-net/postgres-xl,jmcatamney/gpdb,janebeckman/gpdb,ashwinstar/gpdb,rvs/gpdb,pavanvd/postgres-xl,Chibin/gpdb,Postgres-XL/Postgres-XL,royc1/gpdb,Chibin/gpdb,yazun/postgres-xl,foyzur/gpdb,kaknikhil/gpdb,ahachete/gpdb,lpetrov-pivotal/gpdb,rubikloud/gpdb,tangp3/gpdb,adam8157/gpdb,cjcjameson/gpdb,lpetrov-pivotal/gpdb,zaksoup/gpdb,ahachete/gpdb,lpetrov-pivotal/gpdb,edespino/gpdb,lisakowen/gpdb,xuegang/gpdb,kmjungersen/PostgresXL,cjcjameson/gpdb,atris/gpdb,royc1/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,Postgres-XL/Postgres-XL,chrishajas/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,adam8157/gpdb,lintzc/gpdb,yuanzhao/gpdb,snaga/postgres-xl,rubikloud/gpdb,zaksoup/gpdb,lisakowen/gpdb,adam8157/gpdb,ashwinstar/gpdb,ahachete/gpdb,cjcjameson/gpdb,lpetrov-pivotal/gpdb,chrishajas/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,jmcatamney/gpdb,chrishajas/gpdb,rvs/gpdb,tangp3/gpdb,tangp3/gpdb,Quikling/gpdb,atris/gpdb,greenplum-db/gpdb,Quikling/gpdb,arcivanov/postgres-xl,royc1/gpdb,chrishajas/gpdb,edespino/gpdb,lpetrov-pivotal/gpdb,zaksoup/gpdb,xinzweb/gpdb,tangp3/gpdb,CraigHarris/gpdb,CraigHarris/gpdb,50wu/gpdb,ovr/postgres-xl,ovr/postgres-xl,kaknikhil/gpdb,ovr/postgres-xl,zeroae/postgres-xl,snaga/postgres-xl,lintzc/gpdb,snaga/postgres-xl,Chibin/gpdb,yazun/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,tpostgres-projects/tPostgres,rubikloud/gpdb,0x0FFF/gpdb,arcivanov/postgres-xl,adam8157/gpdb,50wu/gpdb,foyzur/gpdb,xuegang/gpdb,atris/gpdb,xuegang/gpdb,edespino/gpdb,cjcjameson/gpdb,arcivanov/postgres-xl,kaknikhil/gpdb,Quikling/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,lpetrov-pivotal/gpdb,lisakowen/gpdb,lisakowen/gpdb,foyzur/gpdb,kmjungersen/PostgresXL,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,pavanvd/postgres-xl,royc1/gpdb,CraigHarris/gpdb,tangp3/gpdb,techdragon/Postgres-XL,zaksoup/gpdb,arcivanov/postgres-xl,ovr/postgres-xl,kaknikhil/gpdb,postmind-net/postgres-xl,kaknikhil/gpdb,chrishajas/gpdb,rvs/gpdb,ashwinstar/gpdb,edespino/gpdb,techdragon/Postgres-XL,tangp3/gpdb,kmjungersen/PostgresXL,lisakowen/gpdb,0x0FFF/gpdb,yuanzhao/gpdb,Quikling/gpdb,CraigHarris/gpdb,rvs/gpdb,rvs/gpdb,kaknikhil/gpdb,xinzweb/gpdb,arcivanov/postgres-xl,yazun/postgres-xl,lisakowen/gpdb,janebeckman/gpdb,yazun/postgres-xl,janebeckman/gpdb,0x0FFF/gpdb,janebeckman/gpdb,kaknikhil/gpdb,foyzur/gpdb,lintzc/gpdb,arcivanov/postgres-xl,zeroae/postgres-xl,postmind-net/postgres-xl,oberstet/postgres-xl,cjcjameson/gpdb,randomtask1155/gpdb,Quikling/gpdb,cjcjameson/gpdb,CraigHarris/gpdb,Chibin/gpdb,CraigHarris/gpdb,greenplum-db/gpdb,chrishajas/gpdb,kmjungersen/PostgresXL,greenplum-db/gpdb,edespino/gpdb,edespino/gpdb,ahachete/gpdb,50wu/gpdb,Quikling/gpdb,lisakowen/gpdb,lintzc/gpdb,foyzur/gpdb,CraigHarris/gpdb,xuegang/gpdb,50wu/gpdb,cjcjameson/gpdb,adam8157/gpdb,0x0FFF/gpdb,randomtask1155/gpdb,edespino/gpdb,lisakowen/gpdb,yuanzhao/gpdb,rubikloud/gpdb,cjcjameson/gpdb,Postgres-XL/Postgres-XL,ahachete/gpdb,royc1/gpdb,foyzur/gpdb,lpetrov-pivotal/gpdb,adam8157/gpdb,Chibin/gpdb,tpostgres-projects/tPostgres,xinzweb/gpdb,Chibin/gpdb,postmind-net/postgres-xl,Quikling/gpdb,janebeckman/gpdb,oberstet/postgres-xl,royc1/gpdb,xuegang/gpdb,kaknikhil/gpdb,edespino/gpdb,snaga/postgres-xl,0x0FFF/gpdb,rubikloud/gpdb,edespino/gpdb,janebeckman/gpdb,randomtask1155/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,xuegang/gpdb,jmcatamney/gpdb,tpostgres-projects/tPostgres,rvs/gpdb,cjcjameson/gpdb,ahachete/gpdb,snaga/postgres-xl,jmcatamney/gpdb,0x0FFF/gpdb,50wu/gpdb,yuanzhao/gpdb,postmind-net/postgres-xl,atris/gpdb,ashwinstar/gpdb,CraigHarris/gpdb,zeroae/postgres-xl,atris/gpdb,ahachete/gpdb,lintzc/gpdb,tpostgres-projects/tPostgres,greenplum-db/gpdb,oberstet/postgres-xl,kaknikhil/gpdb,Chibin/gpdb,janebeckman/gpdb,xinzweb/gpdb,50wu/gpdb,zaksoup/gpdb,50wu/gpdb,rvs/gpdb,xuegang/gpdb,foyzur/gpdb,janebeckman/gpdb,yuanzhao/gpdb,janebeckman/gpdb,randomtask1155/gpdb,kmjungersen/PostgresXL,50wu/gpdb,randomtask1155/gpdb,pavanvd/postgres-xl,zaksoup/gpdb,zaksoup/gpdb,randomtask1155/gpdb,xinzweb/gpdb,lpetrov-pivotal/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,Quikling/gpdb,0x0FFF/gpdb,rubikloud/gpdb,ashwinstar/gpdb,rvs/gpdb,ashwinstar/gpdb,foyzur/gpdb,ovr/postgres-xl,techdragon/Postgres-XL,royc1/gpdb,ahachete/gpdb,xinzweb/gpdb,royc1/gpdb,Chibin/gpdb,rubikloud/gpdb,tangp3/gpdb,rvs/gpdb,randomtask1155/gpdb,lintzc/gpdb,kaknikhil/gpdb,rubikloud/gpdb,zaksoup/gpdb,cjcjameson/gpdb,rvs/gpdb,Postgres-XL/Postgres-XL,lintzc/gpdb,atris/gpdb,lintzc/gpdb,chrishajas/gpdb,xuegang/gpdb,tangp3/gpdb,Chibin/gpdb,yazun/postgres-xl,0x0FFF/gpdb,zeroae/postgres-xl,lintzc/gpdb,Chibin/gpdb,adam8157/gpdb,atris/gpdb,Quikling/gpdb,yuanzhao/gpdb,zeroae/postgres-xl,adam8157/gpdb,xuegang/gpdb,randomtask1155/gpdb,atris/gpdb,yuanzhao/gpdb,edespino/gpdb,chrishajas/gpdb,oberstet/postgres-xl