Fix main README typo.
Fix main README typo.

Brendan Jurd

arcivanov/postgres-xl,adam8157/gpdb,yazun/postgres-xl,50wu/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,snaga/postgres-xl,jmcatamney/gpdb,tpostgres-projects/tPostgres,adam8157/gpdb,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,yazun/postgres-xl,tpostgres-projects/tPostgres,edespino/gpdb,greenplum-db/gpdb,adam8157/gpdb,postmind-net/postgres-xl,lisakowen/gpdb,kmjungersen/PostgresXL,50wu/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,Postgres-XL/Postgres-XL,arcivanov/postgres-xl,jmcatamney/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,xinzweb/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,edespino/gpdb,xinzweb/gpdb,oberstet/postgres-xl,xinzweb/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,ashwinstar/gpdb,edespino/gpdb,postmind-net/postgres-xl,ashwinstar/gpdb,tpostgres-projects/tPostgres,xinzweb/gpdb,Postgres-XL/Postgres-XL,yazun/postgres-xl,edespino/gpdb,50wu/gpdb,ovr/postgres-xl,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,Chibin/gpdb,xinzweb/gpdb,yazun/postgres-xl,edespino/gpdb,edespino/gpdb,lisakowen/gpdb,techdragon/Postgres-XL,tpostgres-projects/tPostgres,snaga/postgres-xl,Chibin/gpdb,ovr/postgres-xl,lisakowen/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,pavanvd/postgres-xl,techdragon/Postgres-XL,snaga/postgres-xl,edespino/gpdb,Postgres-XL/Postgres-XL,postmind-net/postgres-xl,zeroae/postgres-xl,Chibin/gpdb,jmcatamney/gpdb,Chibin/gpdb,oberstet/postgres-xl,yuanzhao/gpdb,arcivanov/postgres-xl,Chibin/gpdb,Chibin/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,ovr/postgres-xl,kmjungersen/PostgresXL,postmind-net/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,50wu/gpdb,Chibin/gpdb,postmind-net/postgres-xl,edespino/gpdb,snaga/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,lisakowen/gpdb,Chibin/gpdb,techdragon/Postgres-XL,50wu/gpdb,edespino/gpdb,yuanzhao/gpdb,lisakowen/gpdb,kmjungersen/PostgresXL,adam8157/gpdb,zeroae/postgres-xl,adam8157/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,ovr/postgres-xl,snaga/postgres-xl,yuanzhao/gpdb,arcivanov/postgres-xl,zeroae/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,yuanzhao/gpdb,lisakowen/gpdb,Chibin/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,tpostgres-projects/tPostgres,50wu/gpdb,yazun/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,kmjungersen/PostgresXL,kmjungersen/PostgresXL,arcivanov/postgres-xl,adam8157/gpdb,ovr/postgres-xl,oberstet/postgres-xl,greenplum-db/gpdb,yuanzhao/gpdb,xinzweb/gpdb,yuanzhao/gpdb,edespino/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,arcivanov/postgres-xl,50wu/gpdb,Chibin/gpdb,pavanvd/postgres-xl