Allow sending Bytes via WebSocket

[carlhoerberg]

Crystal 1.18.0 regression

[ysbaddaden]

I believe other methods that take a message are also affected, such as #pong.

It also means we're missing specs for the bytes case.

[straight-shoota]

We have a spec that tests sending Bytes, but it calls WebSocket::Protocol#send directly instead of the wrapper WebSocket#send 🤷

[straight-shoota]

Actually, WebSocket::Protocol#send (and similar methods) accept any type that responds to #to_slice. So even String | Bytes seems too narrow.
I'm not sure if that's really necessary, and I wouldn't mind narrowing that down and require conversion at the call site if necessary. But that would be a different change.
For now it's probably best just to remove the type restrictions.