Upgrade aiohttp to 3.8.1

[leplatrem]

aio-libs/aiohttp#5905

Fixes crash with:

TypeError: gather() got an unexpected keyword argument 'loop'
(1 additional frame(s) were not displayed)
...
  File "runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "__main__.py", line 6, in <module>
    main(sys.argv[1:])
  File "telescope/app.py", line 478, in main
    web.run_app(app, host=config.HOST, port=config.PORT, print=False)
  File "aiohttp/web.py", line 512, in run_app
    _cancel_tasks({main_task}, loop)
  File "aiohttp/web.py", line 444, in _cancel_tasks
    asyncio.gather(*to_cancel, loop=loop, return_exceptions=True)