scsi: iscsi: Remove unused list 'connlist_err'

I think the last use of this list was removed by
  commit 23d6fef ("scsi: iscsi: Fix in-kernel conn failure
handling").

Build tested only.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Link: https://lore.kernel.org/r/20240503232309.152320-1-linux@treblig.org
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: Dr. David Alan Gilbert

drivers/scsi/scsi_transport_iscsi.c

@@ -1605,7 +1605,6 @@ static DEFINE_MUTEX(rx_queue_mutex);
 static LIST_HEAD(sesslist);
 static DEFINE_SPINLOCK(sesslock);
 static LIST_HEAD(connlist);
-static LIST_HEAD(connlist_err);
 static DEFINE_SPINLOCK(connlock);
 
 static uint32_t iscsi_conn_get_sid(struct iscsi_cls_conn *conn)