doc: Revert ALTER TABLESPACE summary line
doc: Revert ALTER TABLESPACE summary line

It was changed when ALTER TABLESPACE / MOVE was added but then not
updated when that was moved back out.

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