Bump websockets to 11.0.3.

[aaugustin]

Fix #1927.

[aaugustin]

FYI: I tried to remove self.closed_event entirely:

• await self.closed_event.wait() -> await self.wait_closed()
• self.closed_event.is_set() -> self.closed

but it caused another test failure. I didn't investigate further.

[aaugustin]

This change guarantees that the connection handler never exits before the TCP connection is closed. Effectively, this disables websockets' automatic closing handshake, which is clearly the intent of the current implementation (but not always true).

[Kludex]

For the record (for myself), I've tested locally with the application in the test suite:

async def app(scope, receive, send):
    await send({"type": "websocket.accept"})
    return 123

Using a different WebSockets client (wscat):

❯ wscat -c "ws://localhost:8000/"

And I got the same 1006 as before.

[Kludex]

Thanks @aaugustin 🙏