btrfs: remove unused member of btrfs_trans_handle

Last user was removed in a monster commit a22285a6a3
("Btrfs: Integrate metadata reservation with start_transaction") in
2010.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2017-11-08 01:32:48 +01:00
commit 2dbda74ed9