fix: health/alive handler never errors

[alnr]

This is problematic during code generation in downstream projects ever since ory/herodot#106. Since the handler never returns an error (a failing liveness check means you don't get a response at all), the simplest and most correct thing to do is to just not declare an error type at all.

[zepatrik]

The handler itself might not error, but you could e.g. get a 504 or similar. I think you can provide default instead of a status code as well.

[alnr]

The handler itself might not error, but you could e.g. get a 504 or similar. I think you can provide default instead of a status code as well.

updated