[misc] drop coffee-script imports

Gruntfile.js

@@ -16,7 +16,6 @@
  * DS207: Consider shorter variations of null checks
  * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
  */
-const coffee = require('coffee-script')
 const fs = require('fs')
 const { spawn } = require('child_process')
 const { exec } = require('child_process')
@@ -38,7 +37,6 @@ module.exports = function (grunt) {
   grunt.loadNpmTasks('grunt-execute')
   grunt.loadNpmTasks('grunt-available-tasks')
   grunt.loadNpmTasks('grunt-concurrent')
-  grunt.loadNpmTasks('grunt-contrib-coffee')
   grunt.loadNpmTasks('grunt-shell')
 
   grunt.task.loadTasks('./tasks')

package.json

@@ -12,7 +12,6 @@
     "@overleaf/settings": "^2.1.1",
     "async": "^0.9.0",
     "bson": "^1.0.4",
-    "coffee-script": "^1.11.1",
     "east": "0.5.7",
     "east-mongo": "0.3.3",
     "grunt-shell": "^1.1.1",
@@ -41,7 +40,6 @@
     "grunt-execute": "~0.1.5",
     "grunt-available-tasks": "~0.4.1",
     "grunt-concurrent": "~0.4.3",
-    "grunt-contrib-coffee": "~0.10.1",
     "prettier": "^2.2.1",
     "semver": "~2.2.1",
     "knox": "~0.8.9"