Zarr Package Version Requirement

[noahprime]

Noticed this when creating a new venv; the zarr package made an intentional change in their version 3 in how it interacts with fsspec which breaks the fetch_nc function. So for now STITCHES should require zarr version 2.x (or earlier).

Here is discussion on the change: zarr-developers/zarr-python#2706

And here is the effected line of code:

stitches/stitches/fx_pangeo.py

Line 48 in cb8d6ca

mapper = fsspec.get_mapper(zstore)