message: Update promisify types
diff: /**
  @name promisify
  - @signature function promisify (this: ?Object, fn: Function, ...params: Array<mixed>): Promise<mixed>
  + @signature function promisify (this: ?Object, fn: Function, ...params: Array<mixed>): Promise<any>
  @summary Wraps an async callback into a `Promise`
  @description
  Wraps the supplied async function `fn` that has a standard JS callback `(error: Error, result: any)` into a `Promise`, passing the supplied parameters. When `error` is set, the Promise is rejected, else the Promise resolves with the `result` value.
  await promisify(null, (cb) => cb(new Error('error!'))); // rejects with `error!`
  */
  // flowlint-next-line unclear-type:off
  -module.exports = function promisify (self: ?Object, fn: Function, ...params: Array<mixed>): Promise<mixed> {
  +module.exports = function promisify (self: ?Object, fn: Function, ...params: Array<mixed>): Promise<any> {
  return new Promise((resolve, reject) => {
  fn.apply(self, params.concat([
  - (error: ?Error, result: mixed): void => {
  + // flowlint-next-line unclear-type:off
  + (error: ?Error, result: any): void => {
  if (error) {
  reject(error);
  } else {
  