Remove unnecessary parse-analysis error position callback.
Remove unnecessary parse-analysis error position callback.

I guess once upon a time this was needed to get better error messages,
with error positions, but we rely on the 'location' fields in the parse
nodes nowadays. Removing this doesn't affect any of the error messages
memorized in the regression tests, so it's not needed anymore.

50wu/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,edespino/gpdb,ashwinstar/gpdb,janebeckman/gpdb,Chibin/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,janebeckman/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,Chibin/gpdb,edespino/gpdb,xinzweb/gpdb,jmcatamney/gpdb,50wu/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,50wu/gpdb,edespino/gpdb,lisakowen/gpdb,edespino/gpdb,janebeckman/gpdb,xinzweb/gpdb,janebeckman/gpdb,lisakowen/gpdb,Chibin/gpdb,Chibin/gpdb,yuanzhao/gpdb,adam8157/gpdb,lisakowen/gpdb,Chibin/gpdb,janebeckman/gpdb,jmcatamney/gpdb,adam8157/gpdb,janebeckman/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,Chibin/gpdb,greenplum-db/gpdb,50wu/gpdb,jmcatamney/gpdb,lisakowen/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,edespino/gpdb,adam8157/gpdb,janebeckman/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,50wu/gpdb,Chibin/gpdb,xinzweb/gpdb,edespino/gpdb,adam8157/gpdb,janebeckman/gpdb,yuanzhao/gpdb,janebeckman/gpdb,janebeckman/gpdb,adam8157/gpdb,adam8157/gpdb,yuanzhao/gpdb,Chibin/gpdb,yuanzhao/gpdb,edespino/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,edespino/gpdb,xinzweb/gpdb,lisakowen/gpdb,Chibin/gpdb,50wu/gpdb,edespino/gpdb,adam8157/gpdb,adam8157/gpdb,edespino/gpdb,yuanzhao/gpdb,lisakowen/gpdb,ashwinstar/gpdb,Chibin/gpdb