fix: remove VPN backup (service not running)

Removed VPN backup configuration since the VPN service is not currently
included in the compose.yaml and the vpn_etc_wireguard volume doesn't exist.

Kept Netdata backup as those volumes exist and the service is running.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

restic/config.json

@@ -266,22 +266,6 @@
         }
       }
     },
-    {
-      "id": "vpn-backup",
-      "repo": "hidrive-backup",
-      "paths": ["/volumes/vpn_etc_wireguard"],
-      "schedule": {
-        "cron": "0 9 * * *"
-      },
-      "retention": {
-        "policyTimeBucketed": {
-          "daily": 7,
-          "weekly": 4,
-          "monthly": 12,
-          "yearly": 3
-        }
-      }
-    },
     {
       "id": "netdata-backup",
       "repo": "hidrive-backup",