scikit-image warning: `rectangle` is deprecated

[kandersolar]

Recent ci runs show this deprecation warning from scikit-image:

pvanalytics/tests/features/test_shading.py::test_fixed_no_shadows
pvanalytics/tests/features/test_shading.py::test_fixed_same_index
pvanalytics/tests/features/test_shading.py::test_simple_shadow
  D:\a\pvanalytics\pvanalytics\pvanalytics\features\shading.py:368: FutureWarning: `rectangle` is deprecated since version 0.25 and will be removed in version 0.27. Use `skimage.morphology.footprint_rectangle` instead.
    three_minute_mask = morphology.rectangle(1, 3)

Example: https://github.com/pvlib/pvanalytics/actions/runs/12323372696/job/34398845205?pr=215#step:5:45