Remove unused regex import

Co-Authored-By: Simon Li <orpheus+devel@gmail.com>

Author: jacobtomlinson

jupyter_server_proxy/handlers.py

@@ -10,7 +10,6 @@
 from urllib.parse import urlunparse, urlparse
 import aiohttp
 from asyncio import Lock
-import re
 
 from tornado import gen, web, httpclient, httputil, process, websocket, ioloop, version_info