fix: nixos-installer - enable sshd

vars/default.nix

@@ -13,7 +13,7 @@
   #      ```bash
   #      # KDF: bcrypt with 256 rounds, takes 2s on Apple M2):
   #      # Passphrase: digits + letters + symbols, 12+ chars
-  #      ssh-keygen -t ed25519 -a 256 -C "ryan@xxx" -f ~/.ssh/xxx`
+  #      ssh-keygen -t ed25519 -a 256 -C "ryan@xxx" -f ~/.ssh/xxx
   #      ```
   #    2. Never leave the device and never sent over the network.
   # 2. Or just use hardware security keys like Yubikey/CanoKey.