passing `unknown` type via an RPC method results in return type resolving to `never`

### What versions & operating system are you using?

Wranlger 4.27.0

### Please provide a link to a minimal reproduction

https://github.com/repository/workers-never-type-repro

### Describe the Bug

The same also happens with `Fetcher`

```ts
import { WorkerEntrypoint } from "cloudflare:workers";

interface NestedUnknown {
bar: unknown[];
}

class Foo extends WorkerEntrypoint {
public wtf(): unknown {
return;
}

wtf2(): NestedUnknown {
return { bar: [] };
}
}

type TestService = Service;

export default {
async fetch(request, env, ctx): Promise {
const testService = {} as TestService;

// VV this is never type for some reason
const blah = await testService.wtf();

// also this is never type
const nested = await testService.wtf2();

return new Response("Hello World!");
},
} satisfies ExportedHandler;
```

### Please provide any relevant error logs

_No response_