Fix typos in descriptions of json_object functions.
Fix typos in descriptions of json_object functions.

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