Change StatusCode type to ContentfulStatusCode

[thisistonydang]

In the onError handler, returning a c.json() response with a contentless status code will throw a type error, as c.json() requires content. This behavior was introduced in Hono v4.6.15.

To address this, changing the StatusCode type to ContentfulStatusCode in the onError handler should resolve the issue. However, can we safely assume that currentStatus is always a valid status code? Would it be better to maintain an array of valid status codes to check against, rather than simply casting currentStatus to ContentfulStatusCode?