Missing `packaging` dependency

### Zarr version

v3

### Numcodecs version

na

### Python Version

na

### Operating System

na

### Installation

na

### Description

https://github.com/zarr-developers/zarr-python/blob/main/src/zarr/codecs/zstd.py#L10C6-L10C15 import `packaging`, but it's not in our pyproject.toml.

### Steps to reproduce

na

### Additional output

_No response_