btrfs: qgroup: drop unused parameter fs_info from __del_qgroup_rb()

[ Upstream commit 2651f432 ]

We don't need fs_info here, everything is reachable from qgroup.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: e1249667 ("btrfs: qgroup: fix race between quota disable and quota rescan ioctl")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>