btrfs: Remove already completed TODO comment

Fixes: 7cf5b97650 ("btrfs: qgroup: Cleanup old inaccurate facilities")
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -6112,8 +6112,6 @@ void btrfs_delalloc_release_metadata(struct inode *inode, u64 num_bytes)
  * @start: start range we are writing to
  * @len: how long the range we are writing to
  *
- * TODO: This function will finally replace old btrfs_delalloc_reserve_space()
- *
  * This will do the following things
  *
  * o reserve space in data space info for num bytes