fix(PubSub): set max listeners to Infinity

Author: Guillaume Chau

packages/@vue/cli-ui/apollo-server/pubsub.js

@@ -1,5 +1,5 @@
 const { PubSub } = require('graphql-subscriptions')
 
 const pubsub = new PubSub()
-pubsub.ee.setMaxListeners(0)
+pubsub.ee.setMaxListeners(Infinity)
 module.exports = pubsub