Remove synchronous_replication/max_wal_senders cross-check.
Remove synchronous_replication/max_wal_senders cross-check.

This is no longer necessary, and might result in a situation where the
configuration file is reloaded (and everything seems OK) but a subsequent
restart of the database fails.

Per an observation from Fujii Masao.

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