Rules of Durable Objects out-of-date init() method description

### Existing documentation URL(s)

https://developers.cloudflare.com/durable-objects/best-practices/rules-of-durable-objects/#initialize-durable-objects-explicitly-with-an-init-method

### What changes are you suggesting?

This is out of date:
> ### Initialize Durable Objects explicitly with an init() method
> Durable Objects do not know their own name or ID from within. If your Durable Object needs to know its identity (for example, to store a reference to itself or to communicate with related objects), you must explicitly initialize it.

The `ctx: DurableObjectState` property of the `DurableObject` (and constructor parameter) provides the `id`, and (where relevant) `name`. An explicit `init` method is no longer required to know its own identity, but may still be useful for other application-defined identifiers.

### Additional information

_No response_