Remove broken parameter 'table' in wgObjectCaches for CACHE_DB

$wgObjectCaches in DefaultSettings.php had the useless
parameter 'table' for CACHE_DB.
SqlBagOStuff actually uses 'tableName' parameter, it
already defaults to 'objectcache' so there's no need
to write it again.

Change-Id: I5fe6b7c5f4d46cc8642c42861bc7078b795f5fb1