fix for failing numcodecs.zarr3 codecs

[terraputix]

Closes #2900.

I did not add a unit test because it was already mentioned in #2900 that all numcodecs should be better tested in CI, but I guess that belongs into another PR.

You can verify that it works by running the following script:

#!/usr/bin/env -S uv run
# /// script
# requires-python = ">=3.12"
# dependencies = [
#     # "zarr==3.0.2,<3.0.3", # WORKS
#     # "zarr==3.0.4", # FAILS
#     "zarr@git+https://github.com/terraputix/zarr-python.git@8f40aaf3f3fa1d23918520018c60dd0034997f76",  # WORKS
#     "numcodecs==0.15.0",
#     "zfpy==1.0.1",
#     "pcodec==0.3.2",
# ]
# ///
#


import numpy as np
import zarr
zarr.__version__ = "3.0.2"
from numcodecs.zarr3 import ZFPY, PCodec

for serializer in [
    ZFPY(mode=4, tolerance=0.01),
    PCodec(level=8, mode_spec="auto"),
]:
    array = zarr.create_array(
        store=zarr.storage.LocalStore("test"),
        shape=[2, 2],
        chunks=[2, 1],
        dtype=np.float32,
        serializer=serializer,
        compressors=None,
        overwrite=True,
    )
    array[...] = np.array([[0, 1], [2, 3]])

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.rst
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)