documentation/scsi: Remove nodisconnect parameter

The driver that used the 'nodisconnect' parameter was removed in
commit 565bae6a ("[SCSI] 53c7xx: kill driver"). Related documentation
was cleaned up in commit f37a7238 ("[SCSI] 53c7xx: fix removal
fallout"), except for the remaining two mentions that are removed here.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>