btrfs: remove error message from search ioctl for nonexistent tree

Let's remove the error message that appears when the tree_id is not
present. This can happen with the quota tree and has been observed in
practice. The applications are supposed to handle -ENOENT and we don't
need to report that in the system log as it's not a fatal error.
Reported-by: Vlastimil Babka <vbabka@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -2097,8 +2097,6 @@ static noinline int search_ioctl(struct inode *inode,
 		key.offset = (u64)-1;
 		root = btrfs_read_fs_root_no_name(info, &key);
 		if (IS_ERR(root)) {
-			btrfs_err(info, "could not find root %llu",
-			       sk->tree_id);
 			btrfs_free_path(path);
 			return -ENOENT;
 		}