Remove bad kmem_free() oversight from previous zfsdev_state_list patch

I forgot to remove the corresponding kmem_free() from zfs_kmod_fini() in
9a14ce4. Clang's static analyzer did
not complain, but the Coverity scan that was run after the patch was
merged did.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reported-by: Coverity (CID-1535275)
Closes #14556

module/zfs/zfs_ioctl.c

@@ -7862,7 +7862,6 @@ zfs_kmod_fini(void)
 			zfs_onexit_destroy(zs->zs_onexit);
 		if (zs->zs_zevent)
 			zfs_zevent_destroy(zs->zs_zevent);
-		kmem_free(zs, sizeof (zfsdev_state_t));
 	}
 
 	zfs_ereport_taskq_fini();	/* run before zfs_fini() on Linux */