MAINTAINERS: s390/net: remove myself as maintainer

I won't have access to the relevant HW and docs much longer.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Link: https://lore.kernel.org/r/20211209153546.1152921-1-jwi@linux.ibm.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -16623,7 +16623,6 @@ W:	http://www.ibm.com/developerworks/linux/linux390/
 F:	drivers/iommu/s390-iommu.c
 
 S390 IUCV NETWORK LAYER
-M:	Julian Wiedmann <jwi@linux.ibm.com>
 M:	Alexandra Winter <wintera@linux.ibm.com>
 M:	Wenjia Zhang <wenjia@linux.ibm.com>
 L:	linux-s390@vger.kernel.org
@@ -16635,7 +16634,6 @@ F:	include/net/iucv/
 F:	net/iucv/
 
 S390 NETWORK DRIVERS
-M:	Julian Wiedmann <jwi@linux.ibm.com>
 M:	Alexandra Winter <wintera@linux.ibm.com>
 M:	Wenjia Zhang <wenjia@linux.ibm.com>
 L:	linux-s390@vger.kernel.org