Update user-data for autoinstall: disable password login via ssh and remove root password

debian/13-trixie/http/user-data

@@ -6,7 +6,7 @@ autoinstall:
     layout: us
   ssh:
     install-server: true
-    allow-pw: true
+    allow-pw: false
     disable_root: true
     ssh_quiet_keygen: true
     allow_public_ssh_keys: true
@@ -26,7 +26,7 @@ autoinstall:
     users:
       - name: root
         groups: [adm, sudo]
-        lock-passwd: false
+        lock-passwd: true #Disable password login
         sudo: ALL=(ALL) NOPASSWD:ALL
         shell: /bin/bash
-        passwd: packer
+        passwd: "" # Remove password