Rmove optional fields from app.json

Author: kyb3r

app.json

@@ -11,21 +11,9 @@
         "description": "The id for the server you are hosting this bot for.",
         "required": true
     },
-    "PREFIX": {
-        "description": "Command prefix to use, default is `?`",
-        "required": false
-    },
-    "STATUS": {
-        "description": "Set a custom playing status for the bot.",
-        "required": false
-    },
-    "MENTION": {
-        "description": "A custom role/user to mention when creating a modmail thread. Default is @here",
-        "required": false
-    },
     "OWNERS": {
         "description": "Comma seperated user IDs of people that are allowed to use owner only commands. (eval and update)",
-        "required": false
+        "required": true
     },
     "MODMAIL_API_TOKEN": {
         "description": "API token from https://modmail.tk",