Fix outdated comment.
Fix outdated comment.

Commit b3c50e4086 changed the argument from StringInfo to ErrorData *,
but neglected the comment in the header file about it. Fix, by copying
the up-to-date comment from the .c file.

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