Remove mention of password_encryption = plain in postgresql.conf.sample.
Remove mention of password_encryption = plain in postgresql.conf.sample.

Evidently missed in commit eb61136dc.

Spotted by Oleg Bartunov.

Discussion: 19c19e7cb095b18739485541e27a938116a05e15@mail.gmail.com

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