fix: Remove use to event loop policies, removed in Python 3.16

Author: riddell-stan

httpstan/app.py

@@ -3,19 +3,12 @@
 Configure the server and schedule startup and shutdown tasks.
 """
 
-import asyncio
 import logging
 
 import aiohttp.web
 
 import httpstan.routes
 
-try:
-    from uvloop import EventLoopPolicy
-except ImportError:
-    EventLoopPolicy = asyncio.DefaultEventLoopPolicy
-
-
 logger = logging.getLogger("httpstan")