um: Remove unused including <linux/version.h>

Fix the following versioncheck warning:
./arch/um/drivers/vector_kern.c: 11 linux/version.h not needed.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/vector_kern.c

@@ -8,7 +8,6 @@
  * Copyright (C) 2001 by various other people who didn't put their name here.
  */
 
-#include <linux/version.h>
 #include <linux/memblock.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>