MAINTAINERS: Remove defunct iss storage mailing list

It appears that the mailing list email address doesn't exist anymore:

<iss_storagedev@hp.com>: host smtp.hp.com[15.73.96.116] said: 550 5.1.1
    <iss_storagedev@hp.com>: Recipient address rejected: User unknown in
    virtual alias table (in reply to RCPT TO command)
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

MAINTAINERS

@@ -5613,7 +5613,6 @@ F:	drivers/watchdog/hpwdt.c
 
 HEWLETT-PACKARD SMART ARRAY RAID DRIVER (hpsa)
 M:	Don Brace <don.brace@microsemi.com>
-L:	iss_storagedev@hp.com
 L:	esc.storagedev@microsemi.com
 L:	linux-scsi@vger.kernel.org
 S:	Supported
@@ -5624,7 +5623,6 @@ F:	include/uapi/linux/cciss*.h
 
 HEWLETT-PACKARD SMART CISS RAID DRIVER (cciss)
 M:	Don Brace <don.brace@microsemi.com>
-L:	iss_storagedev@hp.com
 L:	esc.storagedev@microsemi.com
 L:	linux-scsi@vger.kernel.org
 S:	Supported