chore(mailserver): update password hashing method

- Changed default hashing method in `mkpasswd` command to `sha-512`.
- Ensures stronger security compared to the previous bcrypt method.

systems/x86_64-linux/mx/mailserver.nix

@@ -1,8 +1,7 @@
-{
-  pkgs,
-  lib,
-  config,
-  ...
+{ pkgs
+, lib
+, config
+, ...
 }:
 {
   # email addresses git smudged
@@ -54,7 +53,7 @@
       ];
     };
     # A list of all login accounts. To create the password hashes, use
-    # nix-shell -p mkpasswd --run 'mkpasswd -sm bcrypt'
+    # nix-shell -p mkpasswd --run 'mkpasswd -m sha-512'
     loginAccounts = {
       "zu@ublre.klm" = {
         hashedPasswordFile = "/ubzr/unenyq/frpergf/zu@ublre.klm";