ARM: shmobile: Remove genmai_defconfig from MAINTAINERS

The genmai defconfig file has been removed by
3ed27bd9 ("ARM: shmobile: genmai: remove defconfig")
so remove its entry in the MAINTAINERS accordingly.
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

MAINTAINERS

@@ -1355,7 +1355,6 @@ F:	arch/arm/boot/dts/sh*
 F:	arch/arm/configs/ape6evm_defconfig
 F:	arch/arm/configs/armadillo800eva_defconfig
 F:	arch/arm/configs/bockw_defconfig
-F:	arch/arm/configs/genmai_defconfig
 F:	arch/arm/configs/koelsch_defconfig
 F:	arch/arm/configs/kzm9g_defconfig
 F:	arch/arm/configs/lager_defconfig