test spopt against the shapely==2.0b1

[jGaboardi]

As per @martinfleis' recommendation, we should test spopt against the shapely pre-release for future-proofing.

# using pip
pip install --pre shapely==2.0b1
# using conda /mamba
conda install -c conda-forge/label/shapely_dev shapely

@martinfleis Do you think testing with an environment locally is sufficient or possibly going as far as adding some environments to the testing matrix?

[martinfleis]

I would add it to CI.

[jGaboardi]

xref pysal/libpysal#482