disable_root: true does not disable ssh login as root user

# Bug report

I created a packer image for Debian 12 with key-based ssh root access for provisioning tasks during the build process.

When creating an instance from this image with Terraform, I want to disable ssh login for the root user and lock the password.

The [documentation](https://cloudinit.readthedocs.io/en/23.4.1/reference/modules.html#ssh) states:
```
disable_root: (boolean) Disable root login. Default: true
```
Therefore I apply the below user_data config in Terraform.

I can see that cloudinit is run, the file /etc/ssh/sshd_config.d/50-cloud-init.conf is created and disables ssh password auth:
```
PasswordAuthentication no
```

But root login using the packer ssh key is still possible. 'PermitRootLogin no' is missing.

## Steps to reproduce the problem
```
#cloud-config
disable_root: true
ssh_pwauth: false

users:
- name: root
lock_passwd: true
- name: ansible
uid: 1000
...
```

## Environment details
- Cloud-init version: 22.4.2-1+deb12u2
- Operating System Distribution: Debian 12
- Cloud provider, platform or installer type: nocloud

## cloud-init logs
[cloud-init.tar.gz](https://github.com/user-attachments/files/18136977/cloud-init.tar.gz)