Fix START_REPLICATION syntax in document.
Fix START_REPLICATION syntax in document.

Enclose "TIMELINE tli" part with brackets because it's optional.

Backport to 9.3 where TIMELINE option was introduced.

Noted by Marko Tiikkaja

pavanvd/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,techdragon/Postgres-XL,50wu/gpdb,lisakowen/gpdb,zeroae/postgres-xl,lisakowen/gpdb,yazun/postgres-xl,adam8157/gpdb,ovr/postgres-xl,50wu/gpdb,pavanvd/postgres-xl,yazun/postgres-xl,techdragon/Postgres-XL,ashwinstar/gpdb,zeroae/postgres-xl,greenplum-db/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,techdragon/Postgres-XL,oberstet/postgres-xl,zeroae/postgres-xl,lisakowen/gpdb,ashwinstar/gpdb,adam8157/gpdb,yazun/postgres-xl,jmcatamney/gpdb,oberstet/postgres-xl,pavanvd/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,techdragon/Postgres-XL,yazun/postgres-xl,zeroae/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,yazun/postgres-xl,50wu/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,oberstet/postgres-xl,50wu/gpdb,pavanvd/postgres-xl,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,ashwinstar/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,50wu/gpdb,zeroae/postgres-xl,lisakowen/gpdb,adam8157/gpdb,greenplum-db/gpdb,xinzweb/gpdb,jmcatamney/gpdb,ovr/postgres-xl,adam8157/gpdb,xinzweb/gpdb,lisakowen/gpdb,ovr/postgres-xl,greenplum-db/gpdb,ovr/postgres-xl,ovr/postgres-xl,xinzweb/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,50wu/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,Postgres-XL/Postgres-XL,Postgres-XL/Postgres-XL,ashwinstar/gpdb,ashwinstar/gpdb,50wu/gpdb,50wu/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,lisakowen/gpdb,jmcatamney/gpdb