remove incorrect release note and add one for the changes here

Author: d-v-b

changes/3638.feature.md

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+The `Store.get` and `Store.get_partial_values` methods now accept `None` as the `prototype` argument. When `prototype` is `None`, stores will use their default buffer class (typically `zarr.core.buffer.cpu.Buffer`). This simplifies the API for common use cases where the default buffer is sufficient.
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+A new type alias `BufferClassLike` has been added, which accepts either a `Buffer` class or a `BufferPrototype` instance.
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+**Breaking change for third-party store implementations:** If you have implemented a custom `Store` subclass, you must update your `get` and `get_partial_values` methods to handle `prototype=None`. To do this, override the `_get_default_buffer_class` method to return an appropriate default `Buffer` class, and update your method signatures to accept `BufferClassLike | None` instead of `BufferPrototype`. When `prototype` is `None`, call `self._get_default_buffer_class()` to obtain the buffer class. If `prototype` is a `BufferPrototype` instance, extract the buffer class via `prototype.buffer`.