btrfs: remove unused qgroup members from btrfs_trans_handle

The members have been effectively unused since "Btrfs: rework qgroup
accounting" (fcebe4562d), there's no substitute for
assert_qgroups_uptodate so it's removed as well.

Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -3003,7 +3003,6 @@ again:
 		goto again;
 	}
 out:
-	assert_qgroups_uptodate(trans);
 	trans->can_flush_pending_bgs = can_flush_pending_bgs;
 	return 0;
 }