Also fix comment in sample postgresql.conf file, for "scram-sha-256".
Also fix comment in sample postgresql.conf file, for "scram-sha-256".

Reported offlist by hubert depesz lubaczewski.

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