Tweak documentation wording to avoid "pdfendlink" failure.
Tweak documentation wording to avoid "pdfendlink" failure.

HEAD documentation was failing to build as US PDF for me, because a link
to "CREATE CAST" was getting split across pages.  Adjust wording to
remove this rather gratuitous cross-reference.

jmcatamney/gpdb,adam8157/gpdb,postmind-net/postgres-xl,zeroae/postgres-xl,kmjungersen/PostgresXL,greenplum-db/gpdb,ashwinstar/gpdb,ovr/postgres-xl,postmind-net/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,oberstet/postgres-xl,lisakowen/gpdb,yazun/postgres-xl,oberstet/postgres-xl,ashwinstar/gpdb,tpostgres-projects/tPostgres,jmcatamney/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,techdragon/Postgres-XL,greenplum-db/gpdb,arcivanov/postgres-xl,yazun/postgres-xl,pavanvd/postgres-xl,xinzweb/gpdb,50wu/gpdb,techdragon/Postgres-XL,50wu/gpdb,snaga/postgres-xl,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,xinzweb/gpdb,postmind-net/postgres-xl,techdragon/Postgres-XL,zeroae/postgres-xl,lisakowen/gpdb,arcivanov/postgres-xl,techdragon/Postgres-XL,adam8157/gpdb,ovr/postgres-xl,arcivanov/postgres-xl,kmjungersen/PostgresXL,ashwinstar/gpdb,kmjungersen/PostgresXL,lisakowen/gpdb,greenplum-db/gpdb,xinzweb/gpdb,jmcatamney/gpdb,arcivanov/postgres-xl,50wu/gpdb,tpostgres-projects/tPostgres,adam8157/gpdb,yazun/postgres-xl,pavanvd/postgres-xl,greenplum-db/gpdb,lisakowen/gpdb,lisakowen/gpdb,kmjungersen/PostgresXL,tpostgres-projects/tPostgres,Postgres-XL/Postgres-XL,zeroae/postgres-xl,snaga/postgres-xl,arcivanov/postgres-xl,greenplum-db/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,adam8157/gpdb,lisakowen/gpdb,jmcatamney/gpdb,arcivanov/postgres-xl,adam8157/gpdb,zeroae/postgres-xl,postmind-net/postgres-xl,jmcatamney/gpdb,snaga/postgres-xl,ovr/postgres-xl,Postgres-XL/Postgres-XL,adam8157/gpdb,greenplum-db/gpdb,snaga/postgres-xl,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,jmcatamney/gpdb,kmjungersen/PostgresXL,tpostgres-projects/tPostgres,ashwinstar/gpdb,adam8157/gpdb,ashwinstar/gpdb,tpostgres-projects/tPostgres,yazun/postgres-xl,lisakowen/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,postmind-net/postgres-xl,pavanvd/postgres-xl,yazun/postgres-xl,ovr/postgres-xl,oberstet/postgres-xl,oberstet/postgres-xl,pavanvd/postgres-xl,50wu/gpdb,jmcatamney/gpdb,ovr/postgres-xl,50wu/gpdb,xinzweb/gpdb,zeroae/postgres-xl,snaga/postgres-xl,50wu/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb,xinzweb/gpdb