btrfs-progs: doc: fix invalid reference to setattr(8)

man 8 btrfs-property refers to `setattr(8)` which does not actually exist.
It should refer to `chattr (1)` instead.

Signed-off-by: Naohiro Aota <naota@elisp.net>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/Documentation/btrfs-property.txt b/Documentation/btrfs-property.txt
index 6b23e2e..9ed568c 100644
--- a/Documentation/btrfs-property.txt
+++ b/Documentation/btrfs-property.txt
@@ -64,4 +64,4 @@
 --------
 `mkfs.btrfs`(8),
 `lsattr`(1),
-`setattr`(8)
+`chattr`(1)