Remove reference to src/tools/backend/index.html
Remove reference to src/tools/backend/index.html

src/tools/backend was removed back in 63f1ccd, but
backend/storage/lmgr/README didn't get the memo.

Author: Amit Langote

50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,xinzweb/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,xinzweb/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,ashwinstar/gpdb,Postgres-XL/Postgres-XL,yazun/postgres-xl,ovr/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,zeroae/postgres-xl,ashwinstar/gpdb,ovr/postgres-xl,adam8157/gpdb,greenplum-db/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,yazun/postgres-xl,techdragon/Postgres-XL,adam8157/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb,yazun/postgres-xl,ovr/postgres-xl,ovr/postgres-xl,techdragon/Postgres-XL,yazun/postgres-xl,50wu/gpdb,zeroae/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,zeroae/postgres-xl,ashwinstar/gpdb,Postgres-XL/Postgres-XL,pavanvd/postgres-xl,xinzweb/gpdb,zeroae/postgres-xl,50wu/gpdb,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,greenplum-db/gpdb,adam8157/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,ovr/postgres-xl,yazun/postgres-xl,oberstet/postgres-xl,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,oberstet/postgres-xl,50wu/gpdb,ashwinstar/gpdb,pavanvd/postgres-xl,pavanvd/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,greenplum-db/gpdb,lisakowen/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,techdragon/Postgres-XL