MAINTAINERS: Make Yu Kuai co-maintainer of md/raid subsystem

In the past couple years, Yu Kuai has been making solid contributions
to md/raid subsystem. Make Yu Kuai a co-maintainer.

Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20241108014112.2098079-1-song@kernel.org
Signed-off-by: Song Liu <song@kernel.org>

Author: liu-song-6

MAINTAINERS

@@ -21303,7 +21303,7 @@ F:	include/linux/property.h
 
 SOFTWARE RAID (Multiple Disks) SUPPORT
 M:	Song Liu <song@kernel.org>
-R:	Yu Kuai <yukuai3@huawei.com>
+M:	Yu Kuai <yukuai3@huawei.com>
 L:	linux-raid@vger.kernel.org
 S:	Supported
 Q:	https://patchwork.kernel.org/project/linux-raid/list/