Deprecation: "arch" parameter got deprecated in API

[The-Judge]

Hetzner deprecated the "arch" parameter in the "POST /boot/{server-number}/rescue" Endpoint.

There is no technical issue here, but it might make sense to remove that from the module to prevent it from becoming an issue in future API versions.

[The-Judge]

@aszlig stated in #60:

I'd rather prefer to emit a DeprecationWarning for now and remove it in the next major version instead to make sure we don't break existing users of the bits kwarg.

So true - will update the PR.