Use WHATWG API

> New application code should use the WHATWG API.

src/remote/activitypub/request.ts

@@ -1,6 +1,5 @@
 import { request } from 'https';
 import { sign } from 'http-signature';
-import { URL } from 'url';
 import * as crypto from 'crypto';
 import { lookup, IRunOptions } from 'lookup-dns-cache';
 import * as promiseAny from 'promise-any';