luksFormat: drop --hash=sha512 argument

The default (sha256) seems fine for LUKS2 where the hash algorithm has a
limited role anyway - it's not used for key stretching like in LUKS1.

user/advanced-topics/secondary-storage.md

@@ -65,7 +65,7 @@ In theory, you can still use file-based disk images ("file" pool driver), but it
 Assuming the secondary hard disk is at /dev/sdb (it will be completely erased), you can set it up for encryption by doing in a dom0 terminal (use the same passphrase as the main Qubes disk to avoid a second password prompt at boot):
 
 ```
-sudo cryptsetup luksFormat --sector-size=512 --hash=sha512 /dev/sdb
+sudo cryptsetup luksFormat --sector-size=512 /dev/sdb
 sudo blkid /dev/sdb
 ```