MAINTAINERS: Remove Jukka Rissanen as 6lowpan maintainer

I no longer work on this so better update the file.
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Link: https://lore.kernel.org/r/20220527075625.9693-1-jukka.rissanen@linux.intel.comSigned-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

MAINTAINERS

@@ -171,7 +171,6 @@ F:	drivers/scsi/53c700*
 
 6LOWPAN GENERIC (BTLE/IEEE 802.15.4)
 M:	Alexander Aring <alex.aring@gmail.com>
-M:	Jukka Rissanen <jukka.rissanen@linux.intel.com>
 L:	linux-bluetooth@vger.kernel.org
 L:	linux-wpan@vger.kernel.org
 S:	Maintained