man: Fix link for --allow-discards option explanation

--allow-discards is documented only in open and refresh man pages
not in luksFormat.

man/cryptsetup.8.adoc

@@ -700,7 +700,7 @@ Albeit Linux kernel 5.7 added TRIM support for standalone dm-integrity devices,
 *cryptsetup(8)* can't offer support for discards (TRIM) in authenticated
 encryption mode, because the underlying dm-crypt kernel module does not support
 this functionality when dm-integrity is used as auth tag space allocator
-(see *--allow-discards* in *cryptsetup-luksFormat(8)*).
+(see *--allow-discards* in *cryptsetup-open(8)*).
 
 Some integrity modes requires two independent keys (key for encryption
 and for authentication). Both these keys are stored in one LUKS keyslot.