[queues] correct DurableObject to DurableObjectNamespace & remove constructor block

[helloimalastair]

In the Env declaration for the Use Queues with Durable Objects example, the YOUR_DO_CLASS binding should be an instance of DurableObjectNamespace instead of DurableObject.

Constructor block for the YourDurableObject class contained an extra }, causing the fetch() to not be recognized. This block has been removed entirely, and the env been made public to match state

[garysassano]

Thanks for the PR.

There's a small snag with the fetch() call. Because it's within an if statement, TypeScript needs a return statement outside the if to cover cases where the condition isn't met. Otherwise, it throws a Function lacks ending return statement and return type does not include 'undefined' error, as the function might not always return the expected Promise<Response>.

[helloimalastair]

@garysassano should be fixed, now returns a 400

[Maddy-Cloudflare]

Better to change the properties to be private.