btrfs: remove stale define after removing ordered operations

Last user removed in commit "btrfs: disable strict file flushes for
renames and truncates" (8d875f95da43c6a8f18f77869f2ef26e9594fecc).

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
1 file changed