MAINTAINERS: remove Ursula Braun as s390 network maintainer

I am retiring soon. Thus this patch removes myself from the
MAINTAINERS file (s390 network).
Signed-off-by: NUrsula Braun <ubraun@linux.ibm.com>
[jwi: fix up the subject]
Signed-off-by: NJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

MAINTAINERS

@@ -15246,7 +15246,6 @@ F:	drivers/iommu/s390-iommu.c
 S390 IUCV NETWORK LAYER
 M:	Julian Wiedmann <jwi@linux.ibm.com>
 M:	Karsten Graul <kgraul@linux.ibm.com>
-M:	Ursula Braun <ubraun@linux.ibm.com>
 L:	linux-s390@vger.kernel.org
 S:	Supported
 W:	http://www.ibm.com/developerworks/linux/linux390/
@@ -15257,7 +15256,6 @@ F:	net/iucv/
 S390 NETWORK DRIVERS
 M:	Julian Wiedmann <jwi@linux.ibm.com>
 M:	Karsten Graul <kgraul@linux.ibm.com>
-M:	Ursula Braun <ubraun@linux.ibm.com>
 L:	linux-s390@vger.kernel.org
 S:	Supported
 W:	http://www.ibm.com/developerworks/linux/linux390/
@@ -15828,7 +15826,6 @@ S:	Maintained
 F:	drivers/misc/sgi-xp/
 
 SHARED MEMORY COMMUNICATIONS (SMC) SOCKETS
-M:	Ursula Braun <ubraun@linux.ibm.com>
 M:	Karsten Graul <kgraul@linux.ibm.com>
 L:	linux-s390@vger.kernel.org
 S:	Supported