Remove Guild from docstring (abalabahaha#257)

Author: macdja38

lib/structures/Message.js

@@ -9,7 +9,6 @@ const User = require("./User");
 * Represents a message
 * @prop {String} id The ID of the message
 * @prop {Channel} channel The channel the message is in
-* @prop {Guild?} guild The guild the message channel is in. Alias to channel.guild
 * @prop {Number} timestamp Timestamp of message creation
 * @prop {Number} type The type of the message
 * @prop {User} author The message author