Wrong case in websocket headers

Server-side capture from a cloudflared-tunneled websocket system:

```
Sec-Websocket-Protocol
```

From the RFC and from native browsers
```
Sec-WebSocket-Protocol
```

Note the case of the S. Affects all websocket headers. While this is technically allowed, it runs into issues with applications expecting exact case from the standard. Since native browsers send the standard's casing, cloudflare's websocket client should too.