Remove RabbitMQ from dependance and config

config-example.json

@@ -111,7 +111,6 @@
   ],
   "session_secret": "@SESSION_SECRET@",
   "judge_token": "@JUDGE_TOKEN@",
-  "rabbitMQ": "amqp://localhost/",
   "redis": "redis://127.0.0.1:6379",
   "email_jwt_secret": "@EMAIL_JWT_SECRET@",
   "google_analytics": "UA-XXXXXXXX-X",

package.json

@@ -23,7 +23,6 @@
   },
   "homepage": "https://github.com/syzoj/syzoj#readme",
   "dependencies": {
-    "amqplib": "^0.5.2",
     "ansi-to-html": "^0.6.10",
     "async-lock": "^1.2.0",
     "body-parser": "^1.15.2",