feat(APIMessage): remove disableMentions (#4836)

* chore: remove disableMentions

* style: fix eslint

test/disableMentions.js

@@ -1,44 +0,0 @@
-'use strict';
-
-const { token, prefix } = require('./auth');
-const Discord = require('../src');
-const { Util } = Discord;
-
-const client = new Discord.Client({
-  // To see a difference, comment out disableMentions and run the same tests using disableEveryone
-  // You will notice that all messages will mention @everyone
-  // disableEveryone: true
-  disableMentions: 'everyone',
-});
-
-const tests = [
-  // Test 1
-  // See https://github.com/discordapp/discord-api-docs/issues/1189
-  '@\u202eeveryone @\u202ehere',
-
-  // Test 2
-  // See https://github.com/discordapp/discord-api-docs/issues/1241
-  // TL;DR: Characters like \u0300 will only be stripped if more than 299 are present
-  `${'\u0300@'.repeat(150)}@\u0300everyone @\u0300here`,
-
-  // Test 3
-  // Normal @everyone/@here mention
-  '@everyone @here',
-];
-
-client.on('ready', () => console.log('Ready!'));
-
-client.on('message', message => {
-  // Check if message starts with prefix
-  if (!message.content.startsWith(prefix)) return;
-  const [command, ...args] = message.content.substr(prefix.length).split(' ');
-
-  // Clean content and log each character
-  console.log(Util.cleanContent(args.join(' '), message).split(''));
-
-  if (command === 'test1') message.channel.send(tests[0]);
-  else if (command === 'test2') message.channel.send(tests[1]);
-  else if (command === 'test3') message.channel.send(tests[2]);
-});
-
-client.login(token).catch(console.error);