remove duplicate enable_proxmox definition (librenms#17803)

Author: Jellyfrog

resources/definitions/config_definitions.json

@@ -2132,10 +2132,6 @@
             "default": false,
             "type": "boolean"
         },
-        "enable_proxmox": {
-            "default": false,
-            "type": "boolean"
-        },
         "enable_ports_adsl": {
             "default": true,
             "type": "boolean"