Update code comment for temporary replication slots
Update code comment for temporary replication slots

Reported-by: Alvaro Herrera <3c84f0de6f8a0f296d36cdd9f57fa166641c96b1@2ndquadrant.com>

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