Remove unneeded polyfill

This polyfill was added because node versions less than 10.5.0 didn't include scrypt support. As we now raised the minimum required version to 12.0.0, this polyfill isn't needed anymore.

Signed-off-by: Erik Michelson <opensource@erik.michelson.eu>

lib/models/user.js

@@ -1,15 +1,6 @@
 'use strict'
 // external modules
 const Sequelize = require('sequelize')
-const crypto = require('crypto')
-if (!crypto.scrypt) {
-  // polyfill for node.js 8.0, see https://github.com/chrisveness/scrypt-kdf#openssl-implementation
-  const scryptAsync = require('scrypt-async')
-  crypto.scrypt = function (password, salt, keylen, options, callback) {
-    const opt = Object.assign({}, options, { dkLen: keylen })
-    scryptAsync(password, salt, opt, (derivedKey) => callback(null, Buffer.from(derivedKey)))
-  }
-}
 const scrypt = require('scrypt-kdf')
 
 // core