Remove leftover 'hyperloglog_counter.sql'.
Remove leftover 'hyperloglog_counter.sql'.

Commit cbe3b08b39 removed the extension that this referred to.

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