only caddy's acme data should be persisted

[iliana]

[root@nixos:~]# tree -a /persist/var/lib/caddy/
/persist/var/lib/caddy/
├── .config
│   └── caddy
│       └── autosave.json
├── .local
│   └── share
│       └── caddy
│           ├── acme
│           │   └── acme-staging-v02.api.letsencrypt.org-directory
│           │       ├── challenge_tokens
│           │       └── users
│           │           └── iliana@oxide.computer
│           │               ├── iliana.json
│           │               └── iliana.key
│           └── locks
└── .step

we don't need .config/caddy/autosave.json because the only valid configuration for the system is the Caddyfile in the nix store, and we never want to be in a situation where autosave.json is getting loaded instead on boot somehow.