Pin numcodecs to <0.16 for unit tests

This was fixed in the latest Zarr 2.18.7 release, but for some reason it doesn't get installed in GitHub actions:
zarr-developers/zarr-python#2963

PiperOrigin-RevId: 750778532

Author: shoyer

setup.py

@@ -38,7 +38,10 @@
 tests_requires = [
     "pytest",
     "pyink",
+    # work around https://github.com/zarr-developers/zarr-python/issues/2963
+    "numcodecs<0.16.0",
 ]
+
 setuptools.setup(
     name="weatherbenchX",
     version="0.0.0",